diff --git a/dom/smil/nsSMILInterval.cpp b/dom/smil/SMILInterval.cpp
similarity index 83%
rename from dom/smil/nsSMILInterval.cpp
rename to dom/smil/SMILInterval.cpp
index 38ec7a972787..a97889eceb08 100644
--- a/dom/smil/nsSMILInterval.cpp
+++ b/dom/smil/SMILInterval.cpp
@@ -4,11 +4,13 @@
  * 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/. */
 
-#include "nsSMILInterval.h"
+#include "SMILInterval.h"
 
-nsSMILInterval::nsSMILInterval() : mBeginFixed(false), mEndFixed(false) {}
+namespace mozilla {
 
-nsSMILInterval::nsSMILInterval(const nsSMILInterval& aOther)
+SMILInterval::SMILInterval() : mBeginFixed(false), mEndFixed(false) {}
+
+SMILInterval::SMILInterval(const SMILInterval& aOther)
     : mBegin(aOther.mBegin),
       mEnd(aOther.mEnd),
       mBeginFixed(false),
@@ -25,13 +27,13 @@ nsSMILInterval::nsSMILInterval(const nsSMILInterval& aOther)
              "Attempt to copy-construct an interval with fixed endpoints");
 }
 
-nsSMILInterval::~nsSMILInterval() {
+SMILInterval::~SMILInterval() {
   MOZ_ASSERT(mDependentTimes.IsEmpty(),
              "Destroying interval without disassociating dependent instance "
              "times. Unlink was not called");
 }
 
-void nsSMILInterval::Unlink(bool aFiltered) {
+void SMILInterval::Unlink(bool aFiltered) {
   for (int32_t i = mDependentTimes.Length() - 1; i >= 0; --i) {
     if (aFiltered) {
       mDependentTimes[i]->HandleFilteredInterval();
@@ -50,17 +52,17 @@ void nsSMILInterval::Unlink(bool aFiltered) {
   mEnd = nullptr;
 }
 
-nsSMILInstanceTime* nsSMILInterval::Begin() {
+nsSMILInstanceTime* SMILInterval::Begin() {
   MOZ_ASSERT(mBegin && mEnd, "Requesting Begin() on un-initialized interval.");
   return mBegin;
 }
 
-nsSMILInstanceTime* nsSMILInterval::End() {
+nsSMILInstanceTime* SMILInterval::End() {
   MOZ_ASSERT(mBegin && mEnd, "Requesting End() on un-initialized interval.");
   return mEnd;
 }
 
-void nsSMILInterval::SetBegin(nsSMILInstanceTime& aBegin) {
+void SMILInterval::SetBegin(nsSMILInstanceTime& aBegin) {
   MOZ_ASSERT(aBegin.Time().IsDefinite(),
              "Attempt to set unresolved or indefinite begin time on interval");
   MOZ_ASSERT(!mBeginFixed,
@@ -74,7 +76,7 @@ void nsSMILInterval::SetBegin(nsSMILInstanceTime& aBegin) {
   mBegin = &aBegin;
 }
 
-void nsSMILInterval::SetEnd(nsSMILInstanceTime& aEnd) {
+void SMILInterval::SetEnd(nsSMILInstanceTime& aEnd) {
   MOZ_ASSERT(!mEndFixed, "Attempt to set end time but the end point is fixed");
   // As with SetBegin, check we're not making an instance time dependent on
   // itself.
@@ -84,14 +86,14 @@ void nsSMILInterval::SetEnd(nsSMILInstanceTime& aEnd) {
   mEnd = &aEnd;
 }
 
-void nsSMILInterval::FixBegin() {
+void SMILInterval::FixBegin() {
   MOZ_ASSERT(mBegin && mEnd, "Fixing begin point on un-initialized interval");
   MOZ_ASSERT(!mBeginFixed, "Duplicate calls to FixBegin()");
   mBeginFixed = true;
   mBegin->AddRefFixedEndpoint();
 }
 
-void nsSMILInterval::FixEnd() {
+void SMILInterval::FixEnd() {
   MOZ_ASSERT(mBegin && mEnd, "Fixing end point on un-initialized interval");
   MOZ_ASSERT(mBeginFixed,
              "Fixing the end of an interval without a fixed begin");
@@ -100,7 +102,7 @@ void nsSMILInterval::FixEnd() {
   mEnd->AddRefFixedEndpoint();
 }
 
-void nsSMILInterval::AddDependentTime(nsSMILInstanceTime& aTime) {
+void SMILInterval::AddDependentTime(nsSMILInstanceTime& aTime) {
   RefPtr<nsSMILInstanceTime>* inserted =
       mDependentTimes.InsertElementSorted(&aTime);
   if (!inserted) {
@@ -108,7 +110,7 @@ void nsSMILInterval::AddDependentTime(nsSMILInstanceTime& aTime) {
   }
 }
 
-void nsSMILInterval::RemoveDependentTime(const nsSMILInstanceTime& aTime) {
+void SMILInterval::RemoveDependentTime(const nsSMILInstanceTime& aTime) {
 #ifdef DEBUG
   bool found =
 #endif
@@ -116,11 +118,11 @@ void nsSMILInterval::RemoveDependentTime(const nsSMILInstanceTime& aTime) {
   MOZ_ASSERT(found, "Couldn't find instance time to delete.");
 }
 
-void nsSMILInterval::GetDependentTimes(InstanceTimeList& aTimes) {
+void SMILInterval::GetDependentTimes(InstanceTimeList& aTimes) {
   aTimes = mDependentTimes;
 }
 
-bool nsSMILInterval::IsDependencyChainLink() const {
+bool SMILInterval::IsDependencyChainLink() const {
   if (!mBegin || !mEnd)
     return false;  // Not yet initialised so it can't be part of a chain
 
@@ -132,3 +134,5 @@ bool nsSMILInterval::IsDependencyChainLink() const {
   return (mBegin->IsDependent() && mBegin->GetBaseInterval() != this) ||
          (mEnd->IsDependent() && mEnd->GetBaseInterval() != this);
 }
+
+}  // namespace mozilla
diff --git a/dom/smil/nsSMILInterval.h b/dom/smil/SMILInterval.h
similarity index 93%
rename from dom/smil/nsSMILInterval.h
rename to dom/smil/SMILInterval.h
index 339cf44a4414..524a126de7b3 100644
--- a/dom/smil/nsSMILInterval.h
+++ b/dom/smil/SMILInterval.h
@@ -10,8 +10,10 @@
 #include "nsSMILInstanceTime.h"
 #include "nsTArray.h"
 
+namespace mozilla {
+
 //----------------------------------------------------------------------
-// nsSMILInterval class
+// SMILInterval class
 //
 // A structure consisting of a begin and end time. The begin time must be
 // resolved (i.e. not indefinite or unresolved).
@@ -19,11 +21,11 @@
 // For an overview of how this class is related to other SMIL time classes see
 // the documentation in nsSMILTimeValue.h
 
-class nsSMILInterval {
+class SMILInterval {
  public:
-  nsSMILInterval();
-  nsSMILInterval(const nsSMILInterval& aOther);
-  ~nsSMILInterval();
+  SMILInterval();
+  SMILInterval(const SMILInterval& aOther);
+  ~SMILInterval();
   void Unlink(bool aFiltered = false);
 
   const nsSMILInstanceTime* Begin() const {
@@ -79,4 +81,6 @@ class nsSMILInterval {
   bool mEndFixed;
 };
 
+}  // namespace mozilla
+
 #endif  // NS_SMILINTERVAL_H_
diff --git a/dom/smil/SMILParserUtils.cpp b/dom/smil/SMILParserUtils.cpp
index cafd57251844..a8555d4c03c3 100644
--- a/dom/smil/SMILParserUtils.cpp
+++ b/dom/smil/SMILParserUtils.cpp
@@ -5,15 +5,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "SMILParserUtils.h"
+
+#include "mozilla/SMILKeySpline.h"
+#include "mozilla/SMILRepeatCount.h"
 #include "mozilla/SVGContentUtils.h"
 #include "mozilla/TextUtils.h"
-#include "SMILKeySpline.h"
 #include "nsISMILAttr.h"
 #include "nsSMILValue.h"
 #include "nsSMILTimeValue.h"
 #include "nsSMILTimeValueSpecParams.h"
 #include "nsSMILTypes.h"
-#include "nsSMILRepeatCount.h"
 #include "nsContentUtils.h"
 #include "nsCharSeparatedTokenizer.h"
 
@@ -551,7 +552,7 @@ bool SMILParserUtils::ParseValuesGeneric(const nsAString& aSpec,
 }
 
 bool SMILParserUtils::ParseRepeatCount(const nsAString& aSpec,
-                                       nsSMILRepeatCount& aResult) {
+                                       SMILRepeatCount& aResult) {
   const nsAString& spec = SMILParserUtils::TrimWhitespace(aSpec);
 
   if (spec.EqualsLiteral("indefinite")) {
diff --git a/dom/smil/SMILParserUtils.h b/dom/smil/SMILParserUtils.h
index 4178e7755532..ae9b2ecd9762 100644
--- a/dom/smil/SMILParserUtils.h
+++ b/dom/smil/SMILParserUtils.h
@@ -11,13 +11,13 @@
 #include "nsStringFwd.h"
 
 class nsISMILAttr;
-class SMILKeySpline;
 class nsSMILTimeValue;
 class nsSMILValue;
-class nsSMILRepeatCount;
 class nsSMILTimeValueSpecParams;
 
 namespace mozilla {
+class SMILKeySpline;
+class SMILRepeatCount;
 namespace dom {
 class SVGAnimationElement;
 }  // namespace dom
@@ -57,7 +57,7 @@ class SMILParserUtils {
                                  GenericValueParser& aParser);
 
   static bool ParseRepeatCount(const nsAString& aSpec,
-                               nsSMILRepeatCount& aResult);
+                               SMILRepeatCount& aResult);
 
   static bool ParseTimeValueSpecParams(const nsAString& aSpec,
                                        nsSMILTimeValueSpecParams& aResult);
diff --git a/dom/smil/nsSMILRepeatCount.cpp b/dom/smil/SMILRepeatCount.cpp
similarity index 62%
rename from dom/smil/nsSMILRepeatCount.cpp
rename to dom/smil/SMILRepeatCount.cpp
index 47754120f49b..ff872855b243 100644
--- a/dom/smil/nsSMILRepeatCount.cpp
+++ b/dom/smil/SMILRepeatCount.cpp
@@ -4,7 +4,12 @@
  * 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/. */
 
-#include "nsSMILRepeatCount.h"
+#include "SMILRepeatCount.h"
+
+namespace mozilla {
+
+/*static*/ const double SMILRepeatCount::kNotSet = -1.0;
+/*static*/ const double SMILRepeatCount::kIndefinite = -2.0;
+
+}  // namespace mozilla
 
-/*static*/ const double nsSMILRepeatCount::kNotSet = -1.0;
-/*static*/ const double nsSMILRepeatCount::kIndefinite = -2.0;
diff --git a/dom/smil/nsSMILRepeatCount.h b/dom/smil/SMILRepeatCount.h
similarity index 83%
rename from dom/smil/nsSMILRepeatCount.h
rename to dom/smil/SMILRepeatCount.h
index 7a5cf2036cba..7e4931252b8f 100644
--- a/dom/smil/nsSMILRepeatCount.h
+++ b/dom/smil/SMILRepeatCount.h
@@ -4,14 +4,16 @@
  * 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 nsSMILRepeatCount_h
-#define nsSMILRepeatCount_h
+#ifndef SMILRepeatCount_h
+#define SMILRepeatCount_h
 
 #include "nsDebug.h"
 #include <math.h>
 
+namespace mozilla {
+
 //----------------------------------------------------------------------
-// nsSMILRepeatCount
+// SMILRepeatCount
 //
 // A tri-state non-negative floating point number for representing the number of
 // times an animation repeat, i.e. the SMIL repeatCount attribute.
@@ -21,10 +23,10 @@
 //  2. set (with non-negative, non-zero count value)
 //  3. indefinite
 //
-class nsSMILRepeatCount {
+class SMILRepeatCount {
  public:
-  nsSMILRepeatCount() : mCount(kNotSet) {}
-  explicit nsSMILRepeatCount(double aCount) : mCount(kNotSet) {
+  SMILRepeatCount() : mCount(kNotSet) {}
+  explicit SMILRepeatCount(double aCount) : mCount(kNotSet) {
     SetCount(aCount);
   }
 
@@ -37,7 +39,7 @@ class nsSMILRepeatCount {
   bool IsIndefinite() const { return mCount == kIndefinite; }
   bool IsSet() const { return mCount != kNotSet; }
 
-  nsSMILRepeatCount& operator=(double aCount) {
+  SMILRepeatCount& operator=(double aCount) {
     SetCount(aCount);
     return *this;
   }
@@ -55,4 +57,6 @@ class nsSMILRepeatCount {
   double mCount;
 };
 
+}  // namespace mozilla
+
 #endif
diff --git a/dom/smil/SMILTimedElement.cpp b/dom/smil/SMILTimedElement.cpp
index e3c80e5f0226..65b564b50e56 100644
--- a/dom/smil/SMILTimedElement.cpp
+++ b/dom/smil/SMILTimedElement.cpp
@@ -548,14 +548,14 @@ void SMILTimedElement::DoSampleAt(nsSMILTime aContainerTime, bool aEndOnly) {
 
     switch (mElementState) {
       case STATE_STARTUP: {
-        nsSMILInterval firstInterval;
+        SMILInterval firstInterval;
         mElementState =
             GetNextInterval(nullptr, nullptr, nullptr, firstInterval)
                 ? STATE_WAITING
                 : STATE_POSTACTIVE;
         stateChanged = true;
         if (mElementState == STATE_WAITING) {
-          mCurrentInterval = MakeUnique<nsSMILInterval>(firstInterval);
+          mCurrentInterval = MakeUnique<SMILInterval>(firstInterval);
           NotifyNewInterval();
         }
       } break;
@@ -592,7 +592,7 @@ void SMILTimedElement::DoSampleAt(nsSMILTime aContainerTime, bool aEndOnly) {
         bool didApplyEarlyEnd = ApplyEarlyEnd(sampleTime);
 
         if (mCurrentInterval->End()->Time() <= sampleTime) {
-          nsSMILInterval newInterval;
+          SMILInterval newInterval;
           mElementState = GetNextInterval(mCurrentInterval.get(), nullptr,
                                           nullptr, newInterval)
                               ? STATE_WAITING
@@ -608,7 +608,7 @@ void SMILTimedElement::DoSampleAt(nsSMILTime aContainerTime, bool aEndOnly) {
           mOldIntervals.AppendElement(std::move(mCurrentInterval));
           SampleFillValue();
           if (mElementState == STATE_WAITING) {
-            mCurrentInterval = MakeUnique<nsSMILInterval>(newInterval);
+            mCurrentInterval = MakeUnique<SMILInterval>(newInterval);
           }
           // We are now in a consistent state to dispatch notifications
           if (didApplyEarlyEnd) {
@@ -950,7 +950,7 @@ nsresult SMILTimedElement::SetRepeatCount(const nsAString& aRepeatCountSpec) {
   // Update the current interval before returning
   AutoIntervalUpdater updater(*this);
 
-  nsSMILRepeatCount newRepeatCount;
+  SMILRepeatCount newRepeatCount;
 
   if (SMILParserUtils::ParseRepeatCount(aRepeatCountSpec, newRepeatCount)) {
     mRepeatCount = newRepeatCount;
@@ -1354,7 +1354,7 @@ void SMILTimedElement::DoPostSeek() {
 }
 
 void SMILTimedElement::UnpreserveInstanceTimes(InstanceTimeList& aList) {
-  const nsSMILInterval* prevInterval = GetPreviousInterval();
+  const SMILInterval* prevInterval = GetPreviousInterval();
   const nsSMILInstanceTime* cutoff =
       mCurrentInterval ? mCurrentInterval->Begin()
                        : prevInterval ? prevInterval->Begin() : nullptr;
@@ -1409,7 +1409,7 @@ void SMILTimedElement::FilterIntervals() {
                            : 0;
   IntervalList filteredList;
   for (uint32_t i = 0; i < mOldIntervals.Length(); ++i) {
-    nsSMILInterval* interval = mOldIntervals[i].get();
+    SMILInterval* interval = mOldIntervals[i].get();
     if (i != 0 &&                         /*skip first interval*/
         i + 1 < mOldIntervals.Length() && /*skip previous interval*/
         (i < threshold || !interval->IsDependencyChainLink())) {
@@ -1477,7 +1477,7 @@ void SMILTimedElement::FilterInstanceTimes(InstanceTimeList& aList) {
     if (mCurrentInterval) {
       timesToKeep.AppendElement(mCurrentInterval->Begin());
     }
-    const nsSMILInterval* prevInterval = GetPreviousInterval();
+    const SMILInterval* prevInterval = GetPreviousInterval();
     if (prevInterval) {
       timesToKeep.AppendElement(prevInterval->End());
     }
@@ -1496,9 +1496,8 @@ void SMILTimedElement::FilterInstanceTimes(InstanceTimeList& aList) {
 // http://www.w3.org/TR/2001/REC-smil-animation-20010904/#Timing-BeginEnd-LC-Start
 //
 bool SMILTimedElement::GetNextInterval(
-    const nsSMILInterval* aPrevInterval,
-    const nsSMILInterval* aReplacedInterval,
-    const nsSMILInstanceTime* aFixedBeginTime, nsSMILInterval& aResult) const {
+    const SMILInterval* aPrevInterval, const SMILInterval* aReplacedInterval,
+    const nsSMILInstanceTime* aFixedBeginTime, SMILInterval& aResult) const {
   MOZ_ASSERT(!aFixedBeginTime || aFixedBeginTime->Time().IsDefinite(),
              "Unresolved or indefinite begin time given for interval start");
   static const nsSMILTimeValue zeroTime(0L);
@@ -1860,13 +1859,13 @@ void SMILTimedElement::UpdateCurrentInterval(bool aForceChangeNotice) {
   // If the interval is active the begin time is fixed.
   const nsSMILInstanceTime* beginTime =
       mElementState == STATE_ACTIVE ? mCurrentInterval->Begin() : nullptr;
-  nsSMILInterval updatedInterval;
+  SMILInterval updatedInterval;
   if (GetNextInterval(GetPreviousInterval(), mCurrentInterval.get(), beginTime,
                       updatedInterval)) {
     if (mElementState == STATE_POSTACTIVE) {
       MOZ_ASSERT(!mCurrentInterval,
                  "In postactive state but the interval has been set");
-      mCurrentInterval = MakeUnique<nsSMILInterval>(updatedInterval);
+      mCurrentInterval = MakeUnique<SMILInterval>(updatedInterval);
       mElementState = STATE_WAITING;
       NotifyNewInterval();
 
@@ -1930,7 +1929,7 @@ void SMILTimedElement::SampleFillValue() {
   nsSMILTime activeTime;
 
   if (mElementState == STATE_WAITING || mElementState == STATE_POSTACTIVE) {
-    const nsSMILInterval* prevInterval = GetPreviousInterval();
+    const SMILInterval* prevInterval = GetPreviousInterval();
     MOZ_ASSERT(prevInterval,
                "Attempting to sample fill value but there is no previous "
                "interval");
@@ -2091,7 +2090,7 @@ void SMILTimedElement::NotifyNewInterval() {
   }
 
   for (auto iter = mTimeDependents.Iter(); !iter.Done(); iter.Next()) {
-    nsSMILInterval* interval = mCurrentInterval.get();
+    SMILInterval* interval = mCurrentInterval.get();
     // It's possible that in notifying one new time dependent of a new interval
     // that a chain reaction is triggered which results in the original
     // interval disappearing. If that's the case we can skip sending further
@@ -2104,7 +2103,7 @@ void SMILTimedElement::NotifyNewInterval() {
   }
 }
 
-void SMILTimedElement::NotifyChangedInterval(nsSMILInterval* aInterval,
+void SMILTimedElement::NotifyChangedInterval(SMILInterval* aInterval,
                                              bool aBeginObjectChanged,
                                              bool aEndObjectChanged) {
   MOZ_ASSERT(aInterval, "Null interval for change notification");
@@ -2144,14 +2143,14 @@ const nsSMILInstanceTime* SMILTimedElement::GetEffectiveBeginInstance() const {
 
     case STATE_WAITING:
     case STATE_POSTACTIVE: {
-      const nsSMILInterval* prevInterval = GetPreviousInterval();
+      const SMILInterval* prevInterval = GetPreviousInterval();
       return prevInterval ? prevInterval->Begin() : nullptr;
     }
   }
   MOZ_CRASH("Invalid element state");
 }
 
-const nsSMILInterval* SMILTimedElement::GetPreviousInterval() const {
+const SMILInterval* SMILTimedElement::GetPreviousInterval() const {
   return mOldIntervals.IsEmpty()
              ? nullptr
              : mOldIntervals[mOldIntervals.Length() - 1].get();
diff --git a/dom/smil/SMILTimedElement.h b/dom/smil/SMILTimedElement.h
index f03123750f8b..3b30dbd5cb08 100644
--- a/dom/smil/SMILTimedElement.h
+++ b/dom/smil/SMILTimedElement.h
@@ -10,11 +10,11 @@
 #include "mozilla/EventForwards.h"
 #include "mozilla/Move.h"
 #include "mozilla/SMILMilestone.h"
+#include "mozilla/SMILInterval.h"
+#include "mozilla/SMILRepeatCount.h"
 #include "mozilla/UniquePtr.h"
-#include "nsSMILInterval.h"
 #include "nsSMILInstanceTime.h"
 #include "nsSMILTimeValueSpec.h"
-#include "nsSMILRepeatCount.h"
 #include "nsSMILTypes.h"
 #include "nsTArray.h"
 #include "nsTHashtable.h"
@@ -348,7 +348,7 @@ class SMILTimedElement {
   // Typedefs
   typedef nsTArray<UniquePtr<nsSMILTimeValueSpec>> TimeValueSpecList;
   typedef nsTArray<RefPtr<nsSMILInstanceTime>> InstanceTimeList;
-  typedef nsTArray<UniquePtr<nsSMILInterval>> IntervalList;
+  typedef nsTArray<UniquePtr<SMILInterval>> IntervalList;
   typedef nsPtrHashKey<nsSMILTimeValueSpec> TimeValueSpecPtrKey;
   typedef nsTHashtable<TimeValueSpecPtrKey> TimeValueSpecHashSet;
 
@@ -459,13 +459,13 @@ class SMILTimedElement {
 
   /**
    * Helper function to iterate through this element's accumulated timing
-   * information (specifically old nsSMILIntervals and nsSMILTimeInstanceTimes)
+   * information (specifically old SMILIntervals and nsSMILTimeInstanceTimes)
    * and discard items that are no longer needed or exceed some threshold of
    * accumulated state.
    */
   void FilterHistory();
 
-  // Helper functions for FilterHistory to clear old nsSMILIntervals and
+  // Helper functions for FilterHistory to clear old SMILIntervals and
   // nsSMILInstanceTimes respectively.
   void FilterIntervals();
   void FilterInstanceTimes(InstanceTimeList& aList);
@@ -492,10 +492,10 @@ class SMILTimedElement {
    *                        returned).
    * @return  true if a suitable interval was found, false otherwise.
    */
-  bool GetNextInterval(const nsSMILInterval* aPrevInterval,
-                       const nsSMILInterval* aReplacedInterval,
+  bool GetNextInterval(const SMILInterval* aPrevInterval,
+                       const SMILInterval* aReplacedInterval,
                        const nsSMILInstanceTime* aFixedBeginTime,
-                       nsSMILInterval& aResult) const;
+                       SMILInterval& aResult) const;
   nsSMILInstanceTime* GetNextGreater(const InstanceTimeList& aList,
                                      const nsSMILTimeValue& aBase,
                                      int32_t& aPosition) const;
@@ -525,12 +525,12 @@ class SMILTimedElement {
   // (ii) after calling these methods we must assume that the state of the
   //      element may have changed.
   void NotifyNewInterval();
-  void NotifyChangedInterval(nsSMILInterval* aInterval,
-                             bool aBeginObjectChanged, bool aEndObjectChanged);
+  void NotifyChangedInterval(SMILInterval* aInterval, bool aBeginObjectChanged,
+                             bool aEndObjectChanged);
 
   void FireTimeEventAsync(EventMessage aMsg, int32_t aDetail);
   const nsSMILInstanceTime* GetEffectiveBeginInstance() const;
-  const nsSMILInterval* GetPreviousInterval() const;
+  const SMILInterval* GetPreviousInterval() const;
   bool HasPlayed() const { return !mOldIntervals.IsEmpty(); }
   bool HasClientInFillRange() const;
   bool EndHasEventConditions() const;
@@ -557,7 +557,7 @@ class SMILTimedElement {
 
   nsSMILTimeValue mSimpleDur;
 
-  nsSMILRepeatCount mRepeatCount;
+  SMILRepeatCount mRepeatCount;
   nsSMILTimeValue mRepeatDur;
 
   nsSMILTimeValue mMin;
@@ -580,7 +580,7 @@ class SMILTimedElement {
   uint32_t mInstanceSerialIndex;
 
   SMILAnimationFunction* mClient;
-  UniquePtr<nsSMILInterval> mCurrentInterval;
+  UniquePtr<SMILInterval> mCurrentInterval;
   IntervalList mOldIntervals;
   uint32_t mCurrentRepeatIteration;
   SMILMilestone mPrevRegisteredMilestone;
diff --git a/dom/smil/moz.build b/dom/smil/moz.build
index d2ad95474b3e..98b75aab3e14 100644
--- a/dom/smil/moz.build
+++ b/dom/smil/moz.build
@@ -12,8 +12,6 @@ MOCHITEST_MANIFESTS += ['test/mochitest.ini']
 EXPORTS += [
     'nsISMILAttr.h',
     'nsSMILInstanceTime.h',
-    'nsSMILInterval.h',
-    'nsSMILRepeatCount.h',
     'nsSMILTimeValue.h',
     'nsSMILTimeValueSpec.h',
     'nsSMILTimeValueSpecParams.h',
@@ -26,10 +24,12 @@ EXPORTS.mozilla += [
     'SMILAnimationFunction.h',
     'SMILCompositorTable.h',
     'SMILCSSValueType.h',
+    'SMILInterval.h',
     'SMILKeySpline.h',
     'SMILMilestone.h',
     'SMILNullType.h',
     'SMILParserUtils.h',
+    'SMILRepeatCount.h',
     'SMILSetAnimationFunction.h',
     'SMILTargetIdentifier.h',
     'SMILTimeContainer.h',
@@ -43,8 +43,6 @@ EXPORTS.mozilla.dom += [
 
 UNIFIED_SOURCES += [
     'nsSMILInstanceTime.cpp',
-    'nsSMILInterval.cpp',
-    'nsSMILRepeatCount.cpp',
     'nsSMILTimeValue.cpp',
     'nsSMILTimeValueSpec.cpp',
     'nsSMILValue.cpp',
@@ -57,9 +55,11 @@ UNIFIED_SOURCES += [
     'SMILEnumType.cpp',
     'SMILFloatType.cpp',
     'SMILIntegerType.cpp',
+    'SMILInterval.cpp',
     'SMILKeySpline.cpp',
     'SMILNullType.cpp',
     'SMILParserUtils.cpp',
+    'SMILRepeatCount.cpp',
     'SMILSetAnimationFunction.cpp',
     'SMILStringType.cpp',
     'SMILTimeContainer.cpp',
diff --git a/dom/smil/nsSMILInstanceTime.cpp b/dom/smil/nsSMILInstanceTime.cpp
index 6b2e603e81d9..a50786dfedab 100644
--- a/dom/smil/nsSMILInstanceTime.cpp
+++ b/dom/smil/nsSMILInstanceTime.cpp
@@ -5,9 +5,10 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsSMILInstanceTime.h"
-#include "nsSMILInterval.h"
-#include "nsSMILTimeValueSpec.h"
+
 #include "mozilla/AutoRestore.h"
+#include "mozilla/SMILInterval.h"
+#include "nsSMILTimeValueSpec.h"
 
 //----------------------------------------------------------------------
 // Implementation
@@ -15,7 +16,7 @@
 nsSMILInstanceTime::nsSMILInstanceTime(const nsSMILTimeValue& aTime,
                                        nsSMILInstanceTimeSource aSource,
                                        nsSMILTimeValueSpec* aCreator,
-                                       nsSMILInterval* aBaseInterval)
+                                       SMILInterval* aBaseInterval)
     : mTime(aTime),
       mFlags(0),
       mVisited(false),
@@ -165,7 +166,7 @@ const nsSMILInstanceTime* nsSMILInstanceTime::GetBaseTime() const {
                                     : mBaseInterval->End();
 }
 
-void nsSMILInstanceTime::SetBaseInterval(nsSMILInterval* aBaseInterval) {
+void nsSMILInstanceTime::SetBaseInterval(SMILInterval* aBaseInterval) {
   MOZ_ASSERT(!mBaseInterval,
              "Attempting to reassociate an instance time with a different "
              "interval.");
diff --git a/dom/smil/nsSMILInstanceTime.h b/dom/smil/nsSMILInstanceTime.h
index ef8f8f60d62b..2686ef323c0f 100644
--- a/dom/smil/nsSMILInstanceTime.h
+++ b/dom/smil/nsSMILInstanceTime.h
@@ -10,10 +10,10 @@
 #include "nsISupportsImpl.h"
 #include "nsSMILTimeValue.h"
 
-class nsSMILInterval;
 class nsSMILTimeValueSpec;
 
 namespace mozilla {
+class SMILInterval;
 class SMILTimeContainer;
 }
 
@@ -29,15 +29,18 @@ class SMILTimeContainer;
 // These objects are owned by an SMILTimedElement but MAY also be referenced
 // by:
 //
-// a) nsSMILIntervals that belong to the same SMILTimedElement and which refer
+// a) SMILIntervals that belong to the same SMILTimedElement and which refer
 //    to the nsSMILInstanceTimes which form the interval endpoints; and/or
-// b) nsSMILIntervals that belong to other SMILTimedElements but which need to
+// b) SMILIntervals that belong to other SMILTimedElements but which need to
 //    update dependent instance times when they change or are deleted.
 //    E.g. for begin='a.begin', 'a' needs to inform dependent
 //    nsSMILInstanceTimes if its begin time changes. This notification is
-//    performed by the nsSMILInterval.
+//    performed by the SMILInterval.
 
 class nsSMILInstanceTime final {
+  typedef mozilla::SMILInterval SMILInterval;
+  typedef mozilla::SMILTimeContainer SMILTimeContainer;
+
  public:
   // Instance time source. Times generated by events, syncbase relationships,
   // and DOM calls behave differently in some circumstances such as when a timed
@@ -56,10 +59,10 @@ class nsSMILInstanceTime final {
   explicit nsSMILInstanceTime(const nsSMILTimeValue& aTime,
                               nsSMILInstanceTimeSource aSource = SOURCE_NONE,
                               nsSMILTimeValueSpec* aCreator = nullptr,
-                              nsSMILInterval* aBaseInterval = nullptr);
+                              SMILInterval* aBaseInterval = nullptr);
 
   void Unlink();
-  void HandleChangedInterval(const mozilla::SMILTimeContainer* aSrcContainer,
+  void HandleChangedInterval(const SMILTimeContainer* aSrcContainer,
                              bool aBeginObjectChanged, bool aEndObjectChanged);
   void HandleDeletedInterval();
   void HandleFilteredInterval();
@@ -85,7 +88,7 @@ class nsSMILInstanceTime final {
 
   bool IsDependent() const { return !!mBaseInterval; }
   bool IsDependentOn(const nsSMILInstanceTime& aOther) const;
-  const nsSMILInterval* GetBaseInterval() const { return mBaseInterval; }
+  const SMILInterval* GetBaseInterval() const { return mBaseInterval; }
   const nsSMILInstanceTime* GetBaseTime() const;
 
   bool SameTimeAndBase(const nsSMILInstanceTime& aOther) const {
@@ -103,7 +106,7 @@ class nsSMILInstanceTime final {
   // Private destructor, to discourage deletion outside of Release():
   ~nsSMILInstanceTime();
 
-  void SetBaseInterval(nsSMILInterval* aBaseInterval);
+  void SetBaseInterval(SMILInterval* aBaseInterval);
 
   nsSMILTimeValue mTime;
 
@@ -159,7 +162,7 @@ class nsSMILInstanceTime final {
   nsSMILTimeValueSpec* mCreator;  // The nsSMILTimeValueSpec object that created
                                   // us. (currently only needed for syncbase
                                   // instance times.)
-  nsSMILInterval* mBaseInterval;  // Interval from which this time is derived
+  SMILInterval* mBaseInterval;    // Interval from which this time is derived
                                   // (only used for syncbase instance times)
 };
 
diff --git a/dom/smil/nsSMILTimeValue.h b/dom/smil/nsSMILTimeValue.h
index aebc793ed3f6..888c2be90cc8 100644
--- a/dom/smil/nsSMILTimeValue.h
+++ b/dom/smil/nsSMILTimeValue.h
@@ -23,7 +23,7 @@
  * nsSMILInstanceTime  -- an nsSMILTimeValue used for constructing intervals. It
  *                        contains additional fields to govern reset behavior
  *                        and track timing dependencies (e.g. syncbase timing).
- * nsSMILInterval      -- a pair of nsSMILInstanceTimes that defines a begin and
+ * SMILInterval        -- a pair of nsSMILInstanceTimes that defines a begin and
  *                        an end time for animation.
  * nsSMILTimeValueSpec -- a component of a begin or end attribute, such as the
  *                        '5s' or 'a.end+2m' in begin="5s; a.end+2m". Acts as
diff --git a/dom/smil/nsSMILTimeValueSpec.cpp b/dom/smil/nsSMILTimeValueSpec.cpp
index 6d4e971da31c..ef738996dd71 100644
--- a/dom/smil/nsSMILTimeValueSpec.cpp
+++ b/dom/smil/nsSMILTimeValueSpec.cpp
@@ -5,6 +5,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/EventListenerManager.h"
+#include "mozilla/SMILInterval.h"
 #include "mozilla/SMILParserUtils.h"
 #include "mozilla/SMILTimeContainer.h"
 #include "mozilla/SMILTimedElement.h"
@@ -12,7 +13,6 @@
 #include "mozilla/dom/SVGAnimationElement.h"
 #include "mozilla/dom/TimeEvent.h"
 #include "nsSMILTimeValueSpec.h"
-#include "nsSMILInterval.h"
 #include "nsSMILTimeValue.h"
 #include "nsSMILInstanceTime.h"
 #include "nsString.h"
@@ -108,7 +108,7 @@ bool nsSMILTimeValueSpec::IsEventBased() const {
 }
 
 void nsSMILTimeValueSpec::HandleNewInterval(
-    nsSMILInterval& aInterval, const SMILTimeContainer* aSrcContainer) {
+    SMILInterval& aInterval, const SMILTimeContainer* aSrcContainer) {
   const nsSMILInstanceTime& baseInstance =
       mParams.mSyncBegin ? *aInterval.Begin() : *aInterval.End();
   nsSMILTimeValue newTime =
diff --git a/dom/smil/nsSMILTimeValueSpec.h b/dom/smil/nsSMILTimeValueSpec.h
index 4c4e8ef7bcb5..985654e91bea 100644
--- a/dom/smil/nsSMILTimeValueSpec.h
+++ b/dom/smil/nsSMILTimeValueSpec.h
@@ -15,9 +15,9 @@
 
 class nsSMILTimeValue;
 class nsSMILInstanceTime;
-class nsSMILInterval;
 
 namespace mozilla {
+class SMILInterval;
 class SMILTimeContainer;
 class SMILTimedElement;
 namespace dom {
@@ -40,6 +40,7 @@ class EventListenerManager;
 
 class nsSMILTimeValueSpec {
  public:
+  typedef mozilla::SMILInterval SMILInterval;
   typedef mozilla::SMILTimeContainer SMILTimeContainer;
   typedef mozilla::SMILTimedElement SMILTimedElement;
   typedef mozilla::dom::Element Element;
@@ -53,7 +54,7 @@ class nsSMILTimeValueSpec {
   void ResolveReferences(Element& aContextElement);
   bool IsEventBased() const;
 
-  void HandleNewInterval(nsSMILInterval& aInterval,
+  void HandleNewInterval(SMILInterval& aInterval,
                          const SMILTimeContainer* aSrcContainer);
   void HandleTargetElementChange(Element* aNewTarget);