diff --git a/dom/bindings/Bindings.conf b/dom/bindings/Bindings.conf
index e5bdd80974fb..ed73bd85838c 100644
--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -1005,10 +1005,6 @@ DOMInterfaces = {
     'headerFile': 'mozilla/dom/SVGGradientElement.h',
 },
 
-'SVGRect': {
-    'nativeType': 'mozilla::dom::SVGIRect'
-},
-
 'SVGStringList': {
     'nativeType': 'mozilla::DOMSVGStringList',
     'headerFile': 'DOMSVGStringList.h',
diff --git a/dom/svg/SVGAnimatedRect.cpp b/dom/svg/SVGAnimatedRect.cpp
index c7118bf41594..f7a4aa00fb00 100644
--- a/dom/svg/SVGAnimatedRect.cpp
+++ b/dom/svg/SVGAnimatedRect.cpp
@@ -7,8 +7,8 @@
 #include "SVGAnimatedRect.h"
 #include "mozilla/dom/SVGAnimatedRectBinding.h"
 #include "mozilla/dom/SVGElement.h"
+#include "mozilla/dom/SVGRect.h"
 #include "SVGAnimatedViewBox.h"
-#include "SVGIRect.h"
 
 namespace mozilla {
 namespace dom {
@@ -26,11 +26,11 @@ SVGAnimatedRect::~SVGAnimatedRect() {
   SVGAnimatedViewBox::sSVGAnimatedRectTearoffTable.RemoveTearoff(mVal);
 }
 
-already_AddRefed<SVGIRect> SVGAnimatedRect::GetBaseVal() {
+already_AddRefed<SVGRect> SVGAnimatedRect::GetBaseVal() {
   return mVal->ToDOMBaseVal(mSVGElement);
 }
 
-already_AddRefed<SVGIRect> SVGAnimatedRect::GetAnimVal() {
+already_AddRefed<SVGRect> SVGAnimatedRect::GetAnimVal() {
   return mVal->ToDOMAnimVal(mSVGElement);
 }
 
diff --git a/dom/svg/SVGAnimatedRect.h b/dom/svg/SVGAnimatedRect.h
index 2f8a532d5ef0..94f4fa52f44d 100644
--- a/dom/svg/SVGAnimatedRect.h
+++ b/dom/svg/SVGAnimatedRect.h
@@ -9,15 +9,21 @@
 
 #include "nsCycleCollectionParticipant.h"
 #include "mozilla/dom/SVGElement.h"
-#include "mozilla/dom/SVGRectBinding.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+
 class SVGAnimatedViewBox;
+
 namespace dom {
 
+class SVGRect;
+
+// Despite the name of this class appearing to be generic,
+// SVGAnimatedRect is only used for viewBox attributes.
+
 class SVGAnimatedRect final : public nsWrapperCache {
  public:
   NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(SVGAnimatedRect)
@@ -30,9 +36,9 @@ class SVGAnimatedRect final : public nsWrapperCache {
   virtual JSObject* WrapObject(JSContext* aCx,
                                JS::Handle<JSObject*> aGivenProto) override;
 
-  already_AddRefed<SVGIRect> GetBaseVal();
+  already_AddRefed<SVGRect> GetBaseVal();
 
-  already_AddRefed<SVGIRect> GetAnimVal();
+  already_AddRefed<SVGRect> GetAnimVal();
 
  private:
   virtual ~SVGAnimatedRect();
diff --git a/dom/svg/SVGAnimatedViewBox.cpp b/dom/svg/SVGAnimatedViewBox.cpp
index 119e125904e7..2ffdd8d7c9d3 100644
--- a/dom/svg/SVGAnimatedViewBox.cpp
+++ b/dom/svg/SVGAnimatedViewBox.cpp
@@ -9,6 +9,7 @@
 #include "mozilla/Move.h"
 #include "mozilla/SMILValue.h"
 #include "mozilla/SVGContentUtils.h"
+#include "mozilla/dom/SVGRect.h"
 #include "nsCharSeparatedTokenizer.h"
 #include "SVGViewBoxSMILType.h"
 #include "nsTextFormatter.h"
@@ -61,32 +62,9 @@ nsresult SVGViewBox::FromString(const nsAString& aStr, SVGViewBox* aViewBox) {
   return NS_OK;
 }
 
-/* Cycle collection macros for SVGAnimatedViewBox */
-
-NS_SVG_VAL_IMPL_CYCLE_COLLECTION_WRAPPERCACHED(SVGAnimatedViewBox::DOMBaseVal,
-                                               mSVGElement)
-NS_SVG_VAL_IMPL_CYCLE_COLLECTION_WRAPPERCACHED(SVGAnimatedViewBox::DOMAnimVal,
-                                               mSVGElement)
-
-NS_IMPL_CYCLE_COLLECTING_ADDREF(SVGAnimatedViewBox::DOMBaseVal)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(SVGAnimatedViewBox::DOMBaseVal)
-
-NS_IMPL_CYCLE_COLLECTING_ADDREF(SVGAnimatedViewBox::DOMAnimVal)
-NS_IMPL_CYCLE_COLLECTING_RELEASE(SVGAnimatedViewBox::DOMAnimVal)
-
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SVGAnimatedViewBox::DOMBaseVal)
-  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_INTERFACE_MAP_ENTRY(nsISupports)
-NS_INTERFACE_MAP_END
-
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SVGAnimatedViewBox::DOMAnimVal)
-  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
-  NS_INTERFACE_MAP_ENTRY(nsISupports)
-NS_INTERFACE_MAP_END
-
-static SVGAttrTearoffTable<SVGAnimatedViewBox, SVGAnimatedViewBox::DOMBaseVal>
+static SVGAttrTearoffTable<SVGAnimatedViewBox, SVGRect>
     sBaseSVGViewBoxTearoffTable;
-static SVGAttrTearoffTable<SVGAnimatedViewBox, SVGAnimatedViewBox::DOMAnimVal>
+static SVGAttrTearoffTable<SVGAnimatedViewBox, SVGRect>
     sAnimSVGViewBoxTearoffTable;
 SVGAttrTearoffTable<SVGAnimatedViewBox, SVGAnimatedRect>
     SVGAnimatedViewBox::sSVGAnimatedRectTearoffTable;
@@ -206,70 +184,45 @@ already_AddRefed<SVGAnimatedRect> SVGAnimatedViewBox::ToSVGAnimatedRect(
   return domAnimatedRect.forget();
 }
 
-already_AddRefed<SVGIRect> SVGAnimatedViewBox::ToDOMBaseVal(
+already_AddRefed<SVGRect> SVGAnimatedViewBox::ToDOMBaseVal(
     SVGElement* aSVGElement) {
   if (!mHasBaseVal || mBaseVal.none) {
     return nullptr;
   }
 
-  RefPtr<DOMBaseVal> domBaseVal = sBaseSVGViewBoxTearoffTable.GetTearoff(this);
+  RefPtr<SVGRect> domBaseVal = sBaseSVGViewBoxTearoffTable.GetTearoff(this);
   if (!domBaseVal) {
-    domBaseVal = new DOMBaseVal(this, aSVGElement);
+    domBaseVal = new SVGRect(this, aSVGElement, SVGRect::BaseValue);
     sBaseSVGViewBoxTearoffTable.AddTearoff(this, domBaseVal);
   }
 
   return domBaseVal.forget();
 }
 
-SVGAnimatedViewBox::DOMBaseVal::~DOMBaseVal() {
-  sBaseSVGViewBoxTearoffTable.RemoveTearoff(mVal);
+SVGRect::~SVGRect() {
+  if (mType == BaseValue) {
+    sBaseSVGViewBoxTearoffTable.RemoveTearoff(mVal);
+  } else if (mType == AnimValue) {
+    sAnimSVGViewBoxTearoffTable.RemoveTearoff(mVal);
+  }
 }
 
-already_AddRefed<SVGIRect> SVGAnimatedViewBox::ToDOMAnimVal(
+already_AddRefed<SVGRect> SVGAnimatedViewBox::ToDOMAnimVal(
     SVGElement* aSVGElement) {
   if ((mAnimVal && mAnimVal->none) ||
       (!mAnimVal && (!mHasBaseVal || mBaseVal.none))) {
     return nullptr;
   }
 
-  RefPtr<DOMAnimVal> domAnimVal = sAnimSVGViewBoxTearoffTable.GetTearoff(this);
+  RefPtr<SVGRect> domAnimVal = sAnimSVGViewBoxTearoffTable.GetTearoff(this);
   if (!domAnimVal) {
-    domAnimVal = new DOMAnimVal(this, aSVGElement);
+    domAnimVal = new SVGRect(this, aSVGElement, SVGRect::AnimValue);
     sAnimSVGViewBoxTearoffTable.AddTearoff(this, domAnimVal);
   }
 
   return domAnimVal.forget();
 }
 
-SVGAnimatedViewBox::DOMAnimVal::~DOMAnimVal() {
-  sAnimSVGViewBoxTearoffTable.RemoveTearoff(mVal);
-}
-
-void SVGAnimatedViewBox::DOMBaseVal::SetX(float aX, ErrorResult& aRv) {
-  SVGViewBox rect = mVal->GetBaseValue();
-  rect.x = aX;
-  mVal->SetBaseValue(rect, mSVGElement);
-}
-
-void SVGAnimatedViewBox::DOMBaseVal::SetY(float aY, ErrorResult& aRv) {
-  SVGViewBox rect = mVal->GetBaseValue();
-  rect.y = aY;
-  mVal->SetBaseValue(rect, mSVGElement);
-}
-
-void SVGAnimatedViewBox::DOMBaseVal::SetWidth(float aWidth, ErrorResult& aRv) {
-  SVGViewBox rect = mVal->GetBaseValue();
-  rect.width = aWidth;
-  mVal->SetBaseValue(rect, mSVGElement);
-}
-
-void SVGAnimatedViewBox::DOMBaseVal::SetHeight(float aHeight,
-                                               ErrorResult& aRv) {
-  SVGViewBox rect = mVal->GetBaseValue();
-  rect.height = aHeight;
-  mVal->SetBaseValue(rect, mSVGElement);
-}
-
 UniquePtr<SMILAttr> SVGAnimatedViewBox::ToSMILAttr(SVGElement* aSVGElement) {
   return MakeUnique<SMILViewBox>(this, aSVGElement);
 }
diff --git a/dom/svg/SVGAnimatedViewBox.h b/dom/svg/SVGAnimatedViewBox.h
index 4424baaf3b05..c8253b7396e1 100644
--- a/dom/svg/SVGAnimatedViewBox.h
+++ b/dom/svg/SVGAnimatedViewBox.h
@@ -15,13 +15,13 @@
 #include "mozilla/SMILAttr.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/dom/SVGAnimatedRect.h"
-#include "mozilla/dom/SVGIRect.h"
 
 namespace mozilla {
 
 class SMILValue;
 
 namespace dom {
+class SVGRect;
 class SVGAnimationElement;
 class SVGElement;
 }  // namespace dom
@@ -80,11 +80,9 @@ class SVGAnimatedViewBox {
   already_AddRefed<mozilla::dom::SVGAnimatedRect> ToSVGAnimatedRect(
       SVGElement* aSVGElement);
 
-  already_AddRefed<mozilla::dom::SVGIRect> ToDOMBaseVal(
-      SVGElement* aSVGElement);
+  already_AddRefed<dom::SVGRect> ToDOMBaseVal(SVGElement* aSVGElement);
 
-  already_AddRefed<mozilla::dom::SVGIRect> ToDOMAnimVal(
-      SVGElement* aSVGElement);
+  already_AddRefed<dom::SVGRect> ToDOMAnimVal(SVGElement* aSVGElement);
 
   mozilla::UniquePtr<SMILAttr> ToSMILAttr(SVGElement* aSVGElement);
 
@@ -94,89 +92,6 @@ class SVGAnimatedViewBox {
   bool mHasBaseVal;
 
  public:
-  struct DOMBaseVal final : public mozilla::dom::SVGIRect {
-    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-    NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(DOMBaseVal)
-
-    DOMBaseVal(SVGAnimatedViewBox* aVal, SVGElement* aSVGElement)
-        : mozilla::dom::SVGIRect(), mVal(aVal), mSVGElement(aSVGElement) {}
-
-    SVGAnimatedViewBox* mVal;  // kept alive because it belongs to content
-    RefPtr<SVGElement> mSVGElement;
-
-    float X() const final { return mVal->GetBaseValue().x; }
-
-    float Y() const final { return mVal->GetBaseValue().y; }
-
-    float Width() const final { return mVal->GetBaseValue().width; }
-
-    float Height() const final { return mVal->GetBaseValue().height; }
-
-    void SetX(float aX, mozilla::ErrorResult& aRv) final;
-    void SetY(float aY, mozilla::ErrorResult& aRv) final;
-    void SetWidth(float aWidth, mozilla::ErrorResult& aRv) final;
-    void SetHeight(float aHeight, mozilla::ErrorResult& aRv) final;
-
-    virtual nsIContent* GetParentObject() const override { return mSVGElement; }
-
-   private:
-    virtual ~DOMBaseVal();
-  };
-
-  struct DOMAnimVal final : public mozilla::dom::SVGIRect {
-    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-    NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(DOMAnimVal)
-
-    DOMAnimVal(SVGAnimatedViewBox* aVal, SVGElement* aSVGElement)
-        : mozilla::dom::SVGIRect(), mVal(aVal), mSVGElement(aSVGElement) {}
-
-    SVGAnimatedViewBox* mVal;  // kept alive because it belongs to content
-    RefPtr<SVGElement> mSVGElement;
-
-    // Script may have modified animation parameters or timeline -- DOM getters
-    // need to flush any resample requests to reflect these modifications.
-    float X() const final {
-      mSVGElement->FlushAnimations();
-      return mVal->GetAnimValue().x;
-    }
-
-    float Y() const final {
-      mSVGElement->FlushAnimations();
-      return mVal->GetAnimValue().y;
-    }
-
-    float Width() const final {
-      mSVGElement->FlushAnimations();
-      return mVal->GetAnimValue().width;
-    }
-
-    float Height() const final {
-      mSVGElement->FlushAnimations();
-      return mVal->GetAnimValue().height;
-    }
-
-    void SetX(float aX, mozilla::ErrorResult& aRv) final {
-      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
-    }
-
-    void SetY(float aY, mozilla::ErrorResult& aRv) final {
-      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
-    }
-
-    void SetWidth(float aWidth, mozilla::ErrorResult& aRv) final {
-      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
-    }
-
-    void SetHeight(float aHeight, mozilla::ErrorResult& aRv) final {
-      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
-    }
-
-    virtual nsIContent* GetParentObject() const override { return mSVGElement; }
-
-   private:
-    virtual ~DOMAnimVal();
-  };
-
   struct SMILViewBox : public SMILAttr {
    public:
     SMILViewBox(SVGAnimatedViewBox* aVal, SVGElement* aSVGElement)
diff --git a/dom/svg/SVGIRect.h b/dom/svg/SVGIRect.h
deleted file mode 100644
index 62055d5309e8..000000000000
--- a/dom/svg/SVGIRect.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef mozilla_dom_SVGIRect_h
-#define mozilla_dom_SVGIRect_h
-
-#include "nsCycleCollectionParticipant.h"
-#include "mozilla/dom/SVGRectBinding.h"
-#include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
-#include "nsWrapperCache.h"
-
-class nsIContent;
-
-namespace mozilla {
-namespace dom {
-
-class SVGIRect : public nsISupports, public nsWrapperCache {
- public:
-  virtual ~SVGIRect() = default;
-
-  JSObject* WrapObject(JSContext* aCx,
-                       JS::Handle<JSObject*> aGivenProto) override {
-    return SVGRect_Binding::Wrap(aCx, this, aGivenProto);
-  }
-
-  virtual nsIContent* GetParentObject() const = 0;
-
-  virtual float X() const = 0;
-
-  virtual void SetX(float aX, ErrorResult& aRv) = 0;
-
-  virtual float Y() const = 0;
-
-  virtual void SetY(float aY, ErrorResult& aRv) = 0;
-
-  virtual float Width() const = 0;
-
-  virtual void SetWidth(float aWidth, ErrorResult& aRv) = 0;
-
-  virtual float Height() const = 0;
-
-  virtual void SetHeight(float aHeight, ErrorResult& aRv) = 0;
-};
-
-}  // namespace dom
-}  // namespace mozilla
-
-#endif  // mozilla_dom_SVGIRect_h
diff --git a/dom/svg/SVGRect.cpp b/dom/svg/SVGRect.cpp
index 946f98edea27..b413e1d83554 100644
--- a/dom/svg/SVGRect.cpp
+++ b/dom/svg/SVGRect.cpp
@@ -5,19 +5,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/dom/SVGRect.h"
-#include "SVGElement.h"
+
+#include "mozilla/dom/SVGRectBinding.h"
+#include "mozilla/dom/SVGSVGElement.h"
+#include "SVGAnimatedViewBox.h"
+#include "nsWrapperCache.h"
 
 using namespace mozilla::gfx;
 
 namespace mozilla {
 namespace dom {
 
-//----------------------------------------------------------------------
-// implementation:
-
-SVGRect::SVGRect(nsIContent* aParent, float x, float y, float w, float h)
-    : SVGIRect(), mParent(aParent), mX(x), mY(y), mWidth(w), mHeight(h) {}
-
 //----------------------------------------------------------------------
 // nsISupports methods:
 
@@ -31,23 +29,132 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(SVGRect)
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
+//----------------------------------------------------------------------
+// implementation:
+
+SVGRect::SVGRect(SVGSVGElement* aSVGElement)
+    : mVal(nullptr), mParent(aSVGElement), mType(CreatedValue) {
+  MOZ_ASSERT(mParent);
+  mRect = gfx::Rect(0, 0, 0, 0);
+}
+
+JSObject* SVGRect::WrapObject(JSContext* aCx,
+                              JS::Handle<JSObject*> aGivenProto) {
+  MOZ_ASSERT(mParent);
+  return SVGRect_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+float SVGRect::X() {
+  switch (mType) {
+    case AnimValue:
+      static_cast<SVGElement*>(mParent->AsElement())->FlushAnimations();
+      return mVal->GetAnimValue().x;
+    case BaseValue:
+      return mVal->GetBaseValue().x;
+    default:
+      return mRect.x;
+  }
+}
+
+float SVGRect::Y() {
+  switch (mType) {
+    case AnimValue:
+      static_cast<SVGElement*>(mParent->AsElement())->FlushAnimations();
+      return mVal->GetAnimValue().y;
+    case BaseValue:
+      return mVal->GetBaseValue().y;
+    default:
+      return mRect.y;
+  }
+}
+
+float SVGRect::Width() {
+  switch (mType) {
+    case AnimValue:
+      static_cast<SVGElement*>(mParent->AsElement())->FlushAnimations();
+      return mVal->GetAnimValue().width;
+    case BaseValue:
+      return mVal->GetBaseValue().width;
+    default:
+      return mRect.width;
+  }
+}
+
+float SVGRect::Height() {
+  switch (mType) {
+    case AnimValue:
+      static_cast<SVGElement*>(mParent->AsElement())->FlushAnimations();
+      return mVal->GetAnimValue().height;
+    case BaseValue:
+      return mVal->GetBaseValue().height;
+    default:
+      return mRect.height;
+  }
+}
+
+void SVGRect::SetX(float aX, ErrorResult& aRv) {
+  switch (mType) {
+    case AnimValue:
+      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+      return;
+    case BaseValue: {
+      SVGViewBox rect = mVal->GetBaseValue();
+      rect.x = aX;
+      mVal->SetBaseValue(rect, static_cast<SVGElement*>(mParent->AsElement()));
+      return;
+    }
+    default:
+      mRect.x = aX;
+  }
+}
+
+void SVGRect::SetY(float aY, ErrorResult& aRv) {
+  switch (mType) {
+    case AnimValue:
+      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+      return;
+    case BaseValue: {
+      SVGViewBox rect = mVal->GetBaseValue();
+      rect.y = aY;
+      mVal->SetBaseValue(rect, static_cast<SVGElement*>(mParent->AsElement()));
+      return;
+    }
+    default:
+      mRect.y = aY;
+  }
+}
+
+void SVGRect::SetWidth(float aWidth, ErrorResult& aRv) {
+  switch (mType) {
+    case AnimValue:
+      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+      return;
+    case BaseValue: {
+      SVGViewBox rect = mVal->GetBaseValue();
+      rect.width = aWidth;
+      mVal->SetBaseValue(rect, static_cast<SVGElement*>(mParent->AsElement()));
+      return;
+    }
+    default:
+      mRect.width = aWidth;
+  }
+}
+
+void SVGRect::SetHeight(float aHeight, ErrorResult& aRv) {
+  switch (mType) {
+    case AnimValue:
+      aRv.Throw(NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR);
+      return;
+    case BaseValue: {
+      SVGViewBox rect = mVal->GetBaseValue();
+      rect.height = aHeight;
+      mVal->SetBaseValue(rect, static_cast<SVGElement*>(mParent->AsElement()));
+      return;
+    }
+    default:
+      mRect.height = aHeight;
+  }
+}
+
 }  // namespace dom
 }  // namespace mozilla
-
-////////////////////////////////////////////////////////////////////////
-// Exported creation functions:
-
-already_AddRefed<mozilla::dom::SVGRect> NS_NewSVGRect(nsIContent* aParent,
-                                                      float aX, float aY,
-                                                      float aWidth,
-                                                      float aHeight) {
-  RefPtr<mozilla::dom::SVGRect> rect =
-      new mozilla::dom::SVGRect(aParent, aX, aY, aWidth, aHeight);
-
-  return rect.forget();
-}
-
-already_AddRefed<mozilla::dom::SVGRect> NS_NewSVGRect(nsIContent* aParent,
-                                                      const Rect& aRect) {
-  return NS_NewSVGRect(aParent, aRect.x, aRect.y, aRect.width, aRect.height);
-}
diff --git a/dom/svg/SVGRect.h b/dom/svg/SVGRect.h
index 6474aefa3783..4875559e04a0 100644
--- a/dom/svg/SVGRect.h
+++ b/dom/svg/SVGRect.h
@@ -7,10 +7,8 @@
 #ifndef mozilla_dom_SVGRect_h
 #define mozilla_dom_SVGRect_h
 
-#include "mozilla/dom/SVGIRect.h"
+#include "mozilla/dom/SVGElement.h"
 #include "mozilla/gfx/Rect.h"
-#include "nsCOMPtr.h"
-#include "SVGElement.h"
 
 ////////////////////////////////////////////////////////////////////////
 // SVGRect class
@@ -18,50 +16,71 @@
 namespace mozilla {
 namespace dom {
 
-class SVGRect final : public SVGIRect {
+class SVGSVGElement;
+
+class SVGRect final : public nsISupports, public nsWrapperCache {
  public:
-  explicit SVGRect(nsIContent* aParent, float x = 0.0f, float y = 0.0f,
-                   float w = 0.0f, float h = 0.0f);
+  typedef enum { BaseValue, AnimValue, CreatedValue } RectType;
 
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(SVGRect)
 
-  // WebIDL
-  float X() const final { return mX; }
+  /**
+   * Generic ctor for objects that are created for an attribute.
+   */
+  SVGRect(SVGAnimatedViewBox* aVal, SVGElement* aSVGElement, RectType aType)
+      : mVal(aVal), mParent(aSVGElement), mType(aType) {
+    MOZ_ASSERT(mParent);
+    MOZ_ASSERT(mType == BaseValue || mType == AnimValue);
+  }
 
-  void SetX(float aX, ErrorResult& aRv) final { mX = aX; }
+  /**
+   * Ctor for creating the objects returned by SVGSVGElement.createSVGRect(),
+   * which do not initially belong to an attribute.
+   */
+  explicit SVGRect(SVGSVGElement* aSVGElement);
 
-  float Y() const final { return mY; }
+  /**
+   * Ctor for all other non-attribute usage i.e getBBox, getExtentOfChar etc.
+   */
+  SVGRect(nsIContent* aParent, const gfx::Rect& aRect)
+      : mVal(nullptr), mRect(aRect), mParent(aParent), mType(CreatedValue) {
+    MOZ_ASSERT(mParent);
+  }
 
-  void SetY(float aY, ErrorResult& aRv) final { mY = aY; }
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
 
-  float Width() const final { return mWidth; }
+  float X();
+  float Y();
+  float Width();
+  float Height();
 
-  void SetWidth(float aWidth, ErrorResult& aRv) final { mWidth = aWidth; }
+  void SetX(float aX, mozilla::ErrorResult& aRv);
+  void SetY(float aY, mozilla::ErrorResult& aRv);
+  void SetWidth(float aWidth, mozilla::ErrorResult& aRv);
+  void SetHeight(float aHeight, mozilla::ErrorResult& aRv);
 
-  float Height() const final { return mHeight; }
+  nsIContent* GetParentObject() const {
+    MOZ_ASSERT(mParent);
+    return mParent;
+  }
 
-  void SetHeight(float aHeight, ErrorResult& aRv) final { mHeight = aHeight; }
+ private:
+  virtual ~SVGRect();
 
-  virtual nsIContent* GetParentObject() const override { return mParent; }
+  // If we're actually representing a viewBox rect then our value
+  // will come from that element's viewBox attribute's value.
+  SVGAnimatedViewBox* mVal;  // kept alive because it belongs to content
+  gfx::Rect mRect;
 
- protected:
-  ~SVGRect() = default;
-
-  nsCOMPtr<nsIContent> mParent;
-  float mX, mY, mWidth, mHeight;
+  // If mType is AnimValue or BaseValue this will be an element that
+  // has a viewBox, otherwise it could be any nsIContent.
+  RefPtr<nsIContent> mParent;
+  const RectType mType;
 };
 
 }  // namespace dom
 }  // namespace mozilla
 
-already_AddRefed<mozilla::dom::SVGRect> NS_NewSVGRect(nsIContent* aParent,
-                                                      float x = 0.0f,
-                                                      float y = 0.0f,
-                                                      float width = 0.0f,
-                                                      float height = 0.0f);
-
-already_AddRefed<mozilla::dom::SVGRect> NS_NewSVGRect(
-    nsIContent* aParent, const mozilla::gfx::Rect& rect);
-
 #endif  // mozilla_dom_SVGRect_h
diff --git a/dom/svg/SVGSVGElement.cpp b/dom/svg/SVGSVGElement.cpp
index f8621817d5c8..4fa882783e73 100644
--- a/dom/svg/SVGSVGElement.cpp
+++ b/dom/svg/SVGSVGElement.cpp
@@ -270,8 +270,8 @@ already_AddRefed<SVGMatrix> SVGSVGElement::CreateSVGMatrix() {
   return do_AddRef(new SVGMatrix());
 }
 
-already_AddRefed<SVGIRect> SVGSVGElement::CreateSVGRect() {
-  return NS_NewSVGRect(this);
+already_AddRefed<SVGRect> SVGSVGElement::CreateSVGRect() {
+  return do_AddRef(new SVGRect(this));
 }
 
 already_AddRefed<DOMSVGTransform> SVGSVGElement::CreateSVGTransform() {
diff --git a/dom/svg/SVGSVGElement.h b/dom/svg/SVGSVGElement.h
index 60b3dfdb689c..7f229ae63acf 100644
--- a/dom/svg/SVGSVGElement.h
+++ b/dom/svg/SVGSVGElement.h
@@ -25,7 +25,7 @@ class DOMSVGAngle;
 class DOMSVGLength;
 class DOMSVGNumber;
 class SVGMatrix;
-class SVGIRect;
+class SVGRect;
 class SVGSVGElement;
 
 // Stores svgView arguments of SVG fragment identifiers.
@@ -137,7 +137,7 @@ class SVGSVGElement final : public SVGSVGElementBase {
   already_AddRefed<DOMSVGAngle> CreateSVGAngle();
   already_AddRefed<nsISVGPoint> CreateSVGPoint();
   already_AddRefed<SVGMatrix> CreateSVGMatrix();
-  already_AddRefed<SVGIRect> CreateSVGRect();
+  already_AddRefed<SVGRect> CreateSVGRect();
   already_AddRefed<DOMSVGTransform> CreateSVGTransform();
   already_AddRefed<DOMSVGTransform> CreateSVGTransformFromMatrix(
       SVGMatrix& matrix);
diff --git a/dom/svg/SVGTextContentElement.cpp b/dom/svg/SVGTextContentElement.cpp
index f1720ad1a857..ad672640dbc1 100644
--- a/dom/svg/SVGTextContentElement.cpp
+++ b/dom/svg/SVGTextContentElement.cpp
@@ -8,7 +8,7 @@
 
 #include "mozilla/dom/SVGLengthBinding.h"
 #include "mozilla/dom/SVGTextContentElementBinding.h"
-#include "mozilla/dom/SVGIRect.h"
+#include "mozilla/dom/SVGRect.h"
 #include "nsBidiUtils.h"
 #include "nsISVGPoint.h"
 #include "nsTextFragment.h"
@@ -163,7 +163,7 @@ already_AddRefed<nsISVGPoint> SVGTextContentElement::GetEndPositionOfChar(
   return point.forget();
 }
 
-already_AddRefed<SVGIRect> SVGTextContentElement::GetExtentOfChar(
+already_AddRefed<SVGRect> SVGTextContentElement::GetExtentOfChar(
     uint32_t charnum, ErrorResult& rv) {
   SVGTextFrame* textFrame = GetSVGTextFrame();
 
@@ -172,7 +172,7 @@ already_AddRefed<SVGIRect> SVGTextContentElement::GetExtentOfChar(
     return nullptr;
   }
 
-  RefPtr<SVGIRect> rect;
+  RefPtr<SVGRect> rect;
   rv = textFrame->GetExtentOfChar(this, charnum, getter_AddRefs(rect));
   return rect.forget();
 }
diff --git a/dom/svg/SVGTextContentElement.h b/dom/svg/SVGTextContentElement.h
index 4c365894a29d..4eec6cb2035c 100644
--- a/dom/svg/SVGTextContentElement.h
+++ b/dom/svg/SVGTextContentElement.h
@@ -20,7 +20,7 @@ class nsISVGPoint;
 namespace dom {
 
 struct DOMPointInit;
-class SVGIRect;
+class SVGRect;
 
 typedef SVGGraphicsElement SVGTextContentElementBase;
 
@@ -46,7 +46,7 @@ class SVGTextContentElement : public SVGTextContentElementBase {
   already_AddRefed<nsISVGPoint> GetEndPositionOfChar(uint32_t charnum,
                                                      ErrorResult& rv);
   MOZ_CAN_RUN_SCRIPT
-  already_AddRefed<SVGIRect> GetExtentOfChar(uint32_t charnum, ErrorResult& rv);
+  already_AddRefed<SVGRect> GetExtentOfChar(uint32_t charnum, ErrorResult& rv);
   MOZ_CAN_RUN_SCRIPT float GetRotationOfChar(uint32_t charnum, ErrorResult& rv);
   MOZ_CAN_RUN_SCRIPT int32_t GetCharNumAtPosition(const DOMPointInit& aPoint);
 
diff --git a/dom/svg/SVGTransformableElement.cpp b/dom/svg/SVGTransformableElement.cpp
index 19591f9906a4..56484b9b2115 100644
--- a/dom/svg/SVGTransformableElement.cpp
+++ b/dom/svg/SVGTransformableElement.cpp
@@ -156,7 +156,7 @@ SVGElement* SVGTransformableElement::GetFarthestViewportElement() {
   return SVGContentUtils::GetOuterSVGElement(this);
 }
 
-already_AddRefed<SVGIRect> SVGTransformableElement::GetBBox(
+already_AddRefed<SVGRect> SVGTransformableElement::GetBBox(
     const SVGBoundingBoxOptions& aOptions, ErrorResult& rv) {
   nsIFrame* frame = GetPrimaryFrame(FlushType::Layout);
 
@@ -199,14 +199,14 @@ already_AddRefed<SVGIRect> SVGTransformableElement::GetBBox(
     rec.x += float(text->GetPosition().x) / AppUnitsPerCSSPixel();
     rec.y += float(text->GetPosition().y) / AppUnitsPerCSSPixel();
 
-    return NS_NewSVGRect(this, ToRect(rec));
+    return do_AddRef(new SVGRect(this, ToRect(rec)));
   }
 
   if (!NS_SVGNewGetBBoxEnabled()) {
-    return NS_NewSVGRect(
+    return do_AddRef(new SVGRect(
         this, ToRect(nsSVGUtils::GetBBox(
                   frame, nsSVGUtils::eBBoxIncludeFillGeometry |
-                             nsSVGUtils::eUseUserSpaceOfUseElement)));
+                             nsSVGUtils::eUseUserSpaceOfUseElement))));
   }
   uint32_t flags = 0;
   if (aOptions.mFill) {
@@ -222,14 +222,15 @@ already_AddRefed<SVGIRect> SVGTransformableElement::GetBBox(
     flags |= nsSVGUtils::eBBoxIncludeClipped;
   }
   if (flags == 0) {
-    return NS_NewSVGRect(this, 0, 0, 0, 0);
+    return do_AddRef(new SVGRect(this, gfx::Rect()));
   }
   if (flags == nsSVGUtils::eBBoxIncludeMarkers ||
       flags == nsSVGUtils::eBBoxIncludeClipped) {
     flags |= nsSVGUtils::eBBoxIncludeFill;
   }
   flags |= nsSVGUtils::eUseUserSpaceOfUseElement;
-  return NS_NewSVGRect(this, ToRect(nsSVGUtils::GetBBox(frame, flags)));
+  return do_AddRef(
+      new SVGRect(this, ToRect(nsSVGUtils::GetBBox(frame, flags))));
 }
 
 already_AddRefed<SVGMatrix> SVGTransformableElement::GetCTM() {
diff --git a/dom/svg/SVGTransformableElement.h b/dom/svg/SVGTransformableElement.h
index 2a3adce9a44f..35860e0669fe 100644
--- a/dom/svg/SVGTransformableElement.h
+++ b/dom/svg/SVGTransformableElement.h
@@ -20,7 +20,7 @@ namespace dom {
 class DOMSVGAnimatedTransformList;
 class SVGGraphicsElement;
 class SVGMatrix;
-class SVGIRect;
+class SVGRect;
 struct SVGBoundingBoxOptions;
 
 class SVGTransformableElement : public SVGElement {
@@ -36,8 +36,8 @@ class SVGTransformableElement : public SVGElement {
   SVGElement* GetNearestViewportElement();
   SVGElement* GetFarthestViewportElement();
   MOZ_CAN_RUN_SCRIPT
-  already_AddRefed<SVGIRect> GetBBox(const SVGBoundingBoxOptions& aOptions,
-                                     ErrorResult& rv);
+  already_AddRefed<SVGRect> GetBBox(const SVGBoundingBoxOptions& aOptions,
+                                    ErrorResult& rv);
   already_AddRefed<SVGMatrix> GetCTM();
   already_AddRefed<SVGMatrix> GetScreenCTM();
   already_AddRefed<SVGMatrix> GetTransformToElement(
diff --git a/dom/svg/moz.build b/dom/svg/moz.build
index e55c39a28419..ab6682c497e3 100644
--- a/dom/svg/moz.build
+++ b/dom/svg/moz.build
@@ -62,7 +62,6 @@ EXPORTS.mozilla.dom += [
     'SVGGradientElement.h',
     'SVGGraphicsElement.h',
     'SVGImageElement.h',
-    'SVGIRect.h',
     'SVGLineElement.h',
     'SVGMarkerElement.h',
     'SVGMaskElement.h',
diff --git a/layout/svg/SVGTextFrame.cpp b/layout/svg/SVGTextFrame.cpp
index f26aa75136b1..d5762fe68a2f 100644
--- a/layout/svg/SVGTextFrame.cpp
+++ b/layout/svg/SVGTextFrame.cpp
@@ -4035,7 +4035,7 @@ nsresult SVGTextFrame::GetEndPositionOfChar(nsIContent* aContent,
  * text content element.
  */
 nsresult SVGTextFrame::GetExtentOfChar(nsIContent* aContent, uint32_t aCharNum,
-                                       SVGIRect** aResult) {
+                                       SVGRect** aResult) {
   nsIFrame* kid = PrincipalChildList().FirstChild();
   if (NS_SUBTREE_DIRTY(kid)) {
     // We're never reflowed if we're under a non-SVG element that is
@@ -4088,7 +4088,7 @@ nsresult SVGTextFrame::GetExtentOfChar(nsIContent* aContent, uint32_t aCharNum,
   // Transform the glyph's rect into user space.
   gfxRect r = m.TransformBounds(glyphRect);
 
-  RefPtr<SVGRect> rect = new SVGRect(aContent, r.x, r.y, r.width, r.height);
+  RefPtr<SVGRect> rect = new SVGRect(aContent, ToRect(r));
   rect.forget(aResult);
   return NS_OK;
 }
diff --git a/layout/svg/SVGTextFrame.h b/layout/svg/SVGTextFrame.h
index 5b46e7242476..e3060d14f8a0 100644
--- a/layout/svg/SVGTextFrame.h
+++ b/layout/svg/SVGTextFrame.h
@@ -35,7 +35,7 @@ class TextRenderedRunIterator;
 
 namespace dom {
 struct DOMPointInit;
-class SVGIRect;
+class SVGRect;
 class SVGGeometryElement;
 }  // namespace dom
 
@@ -247,7 +247,7 @@ class SVGTextFrame final : public nsSVGDisplayContainerFrame {
   nsresult GetEndPositionOfChar(nsIContent* aContent, uint32_t aCharNum,
                                 mozilla::nsISVGPoint** aResult);
   nsresult GetExtentOfChar(nsIContent* aContent, uint32_t aCharNum,
-                           mozilla::dom::SVGIRect** aResult);
+                           mozilla::dom::SVGRect** aResult);
   nsresult GetRotationOfChar(nsIContent* aContent, uint32_t aCharNum,
                              float* aResult);