diff --git a/content/base/public/BlobSet.h b/content/base/public/BlobSet.h
new file mode 100644
index 000000000000..198e80850b43
--- /dev/null
+++ b/content/base/public/BlobSet.h
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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_BlobSet_h
+#define mozilla_dom_BlobSet_h
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/dom/File.h"
+
+namespace mozilla {
+namespace dom {
+
+class BlobSet {
+public:
+  BlobSet()
+    : mData(nullptr), mDataLen(0), mDataBufferLen(0)
+  {}
+
+  ~BlobSet()
+  {
+    moz_free(mData);
+  }
+
+  nsresult AppendVoidPtr(const void* aData, uint32_t aLength);
+  nsresult AppendString(const nsAString& aString, bool nativeEOL, JSContext* aCx);
+  nsresult AppendBlobImpl(FileImpl* aBlobImpl);
+  nsresult AppendBlobImpls(const nsTArray<nsRefPtr<FileImpl>>& aBlobImpls);
+
+  nsTArray<nsRefPtr<FileImpl>>& GetBlobImpls() { Flush(); return mBlobImpls; }
+
+  already_AddRefed<File> GetBlobInternal(nsISupports* aParent,
+                                         const nsACString& aContentType);
+
+protected:
+  bool ExpandBufferSize(uint64_t aSize)
+  {
+    using mozilla::CheckedUint32;
+
+    if (mDataBufferLen >= mDataLen + aSize) {
+      mDataLen += aSize;
+      return true;
+    }
+
+    // Start at 1 or we'll loop forever.
+    CheckedUint32 bufferLen =
+      std::max<uint32_t>(static_cast<uint32_t>(mDataBufferLen), 1);
+    while (bufferLen.isValid() && bufferLen.value() < mDataLen + aSize)
+      bufferLen *= 2;
+
+    if (!bufferLen.isValid())
+      return false;
+
+    void* data = moz_realloc(mData, bufferLen.value());
+    if (!data)
+      return false;
+
+    mData = data;
+    mDataBufferLen = bufferLen.value();
+    mDataLen += aSize;
+    return true;
+  }
+
+  void Flush() {
+    if (mData) {
+      // If we have some data, create a blob for it
+      // and put it on the stack
+
+      nsRefPtr<FileImpl> blobImpl =
+        new FileImplMemory(mData, mDataLen, EmptyString());
+      mBlobImpls.AppendElement(blobImpl);
+      mData = nullptr; // The nsDOMMemoryFile takes ownership of the buffer
+      mDataLen = 0;
+      mDataBufferLen = 0;
+    }
+  }
+
+  nsTArray<nsRefPtr<FileImpl>> mBlobImpls;
+  void* mData;
+  uint64_t mDataLen;
+  uint64_t mDataBufferLen;
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_BlobSet_h
diff --git a/content/base/public/File.h b/content/base/public/File.h
index 44e991d09b4d..d7a1d88674dd 100644
--- a/content/base/public/File.h
+++ b/content/base/public/File.h
@@ -58,9 +58,6 @@ struct BlobPropertyBag;
 struct FilePropertyBag;
 class FileImpl;
 
-/* FOLLOWUP TODO:
-1. remove nsDOMBlobBuilder.h
-*/
 class File MOZ_FINAL : public nsIDOMFile
                      , public nsIXHRSendable
                      , public nsIMutable
diff --git a/content/base/public/moz.build b/content/base/public/moz.build
index 49a74d15b0a7..c0dad7074ca0 100644
--- a/content/base/public/moz.build
+++ b/content/base/public/moz.build
@@ -66,6 +66,7 @@ EXPORTS += [
 ]
 
 EXPORTS.mozilla.dom += [
+    'BlobSet.h',
     'DirectionalityUtils.h',
     'Element.h',
     'ElementInlines.h',
diff --git a/content/base/src/File.cpp b/content/base/src/File.cpp
index c6372b1ed974..6c737cbd60e4 100644
--- a/content/base/src/File.cpp
+++ b/content/base/src/File.cpp
@@ -6,10 +6,10 @@
 
 #include "mozilla/dom/File.h"
 
+#include "MultipartFileImpl.h"
 #include "nsCExternalHandlerService.h"
 #include "nsContentCID.h"
 #include "nsContentUtils.h"
-#include "nsDOMBlobBuilder.h"
 #include "nsError.h"
 #include "nsICharsetDetector.h"
 #include "nsIConverterInputStream.h"
@@ -35,6 +35,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/dom/BlobBinding.h"
+#include "mozilla/dom/BlobSet.h"
 #include "mozilla/dom/DOMError.h"
 #include "mozilla/dom/FileBinding.h"
 #include "mozilla/dom/WorkerPrivate.h"
@@ -1237,5 +1238,70 @@ FileList::Item(uint32_t aIndex, nsIDOMFile **aFile)
   return NS_OK;
 }
 
+////////////////////////////////////////////////////////////////////////////
+// BlobSet implementation
+
+already_AddRefed<File>
+BlobSet::GetBlobInternal(nsISupports* aParent, const nsACString& aContentType)
+{
+  nsRefPtr<File> blob = new File(aParent,
+    new MultipartFileImpl(GetBlobImpls(),
+                          NS_ConvertASCIItoUTF16(aContentType)));
+  return blob.forget();
+}
+
+nsresult
+BlobSet::AppendVoidPtr(const void* aData, uint32_t aLength)
+{
+  NS_ENSURE_ARG_POINTER(aData);
+
+  uint64_t offset = mDataLen;
+
+  if (!ExpandBufferSize(aLength))
+    return NS_ERROR_OUT_OF_MEMORY;
+
+  memcpy((char*)mData + offset, aData, aLength);
+  return NS_OK;
+}
+
+nsresult
+BlobSet::AppendString(const nsAString& aString, bool nativeEOL, JSContext* aCx)
+{
+  nsCString utf8Str = NS_ConvertUTF16toUTF8(aString);
+
+  if (nativeEOL) {
+    if (utf8Str.FindChar('\r') != kNotFound) {
+      utf8Str.ReplaceSubstring("\r\n", "\n");
+      utf8Str.ReplaceSubstring("\r", "\n");
+    }
+#ifdef XP_WIN
+    utf8Str.ReplaceSubstring("\n", "\r\n");
+#endif
+  }
+
+  return AppendVoidPtr((void*)utf8Str.Data(),
+                       utf8Str.Length());
+}
+
+nsresult
+BlobSet::AppendBlobImpl(FileImpl* aBlobImpl)
+{
+  NS_ENSURE_ARG_POINTER(aBlobImpl);
+
+  Flush();
+  mBlobImpls.AppendElement(aBlobImpl);
+
+  return NS_OK;
+}
+
+nsresult
+BlobSet::AppendBlobImpls(const nsTArray<nsRefPtr<FileImpl>>& aBlobImpls)
+{
+  Flush();
+  mBlobImpls.AppendElements(aBlobImpls);
+
+  return NS_OK;
+}
+
 } // dom namespace
 } // mozilla namespace
diff --git a/content/base/src/nsDOMBlobBuilder.cpp b/content/base/src/MultipartFileImpl.cpp
similarity index 89%
rename from content/base/src/nsDOMBlobBuilder.cpp
rename to content/base/src/MultipartFileImpl.cpp
index 18f4d2ba09cb..4de8f88d9011 100644
--- a/content/base/src/nsDOMBlobBuilder.cpp
+++ b/content/base/src/MultipartFileImpl.cpp
@@ -3,8 +3,9 @@
  * 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 "nsDOMBlobBuilder.h"
+#include "MultipartFileImpl.h"
 #include "jsfriendapi.h"
+#include "mozilla/dom/BlobSet.h"
 #include "mozilla/dom/FileBinding.h"
 #include "nsAutoPtr.h"
 #include "nsDOMClassInfoID.h"
@@ -350,56 +351,3 @@ MultipartFileImpl::InitializeChromeFile(nsPIDOMWindow* aWindow,
 
   InitializeChromeFile(aWindow, file, aBag, false, aRv);
 }
-
-nsresult
-BlobSet::AppendVoidPtr(const void* aData, uint32_t aLength)
-{
-  NS_ENSURE_ARG_POINTER(aData);
-
-  uint64_t offset = mDataLen;
-
-  if (!ExpandBufferSize(aLength))
-    return NS_ERROR_OUT_OF_MEMORY;
-
-  memcpy((char*)mData + offset, aData, aLength);
-  return NS_OK;
-}
-
-nsresult
-BlobSet::AppendString(const nsAString& aString, bool aNativeEOL, JSContext* aCx)
-{
-  NS_ConvertUTF16toUTF8 utf8Str(aString);
-
-  if (aNativeEOL) {
-    if (utf8Str.FindChar('\r') != kNotFound) {
-      utf8Str.ReplaceSubstring("\r\n", "\n");
-      utf8Str.ReplaceSubstring("\r", "\n");
-    }
-#ifdef XP_WIN
-    utf8Str.ReplaceSubstring("\n", "\r\n");
-#endif
-  }
-
-  return AppendVoidPtr((void*)utf8Str.Data(),
-                       utf8Str.Length());
-}
-
-nsresult
-BlobSet::AppendBlobImpl(FileImpl* aBlobImpl)
-{
-  NS_ENSURE_ARG_POINTER(aBlobImpl);
-
-  Flush();
-  mBlobImpls.AppendElement(aBlobImpl);
-
-  return NS_OK;
-}
-
-nsresult
-BlobSet::AppendBlobImpls(const nsTArray<nsRefPtr<FileImpl>>& aBlobImpls)
-{
-  Flush();
-  mBlobImpls.AppendElements(aBlobImpls);
-
-  return NS_OK;
-}
diff --git a/content/base/src/nsDOMBlobBuilder.h b/content/base/src/MultipartFileImpl.h
similarity index 62%
rename from content/base/src/nsDOMBlobBuilder.h
rename to content/base/src/MultipartFileImpl.h
index 9e238eb86131..7173f51766bf 100644
--- a/content/base/src/nsDOMBlobBuilder.h
+++ b/content/base/src/MultipartFileImpl.h
@@ -3,8 +3,8 @@
  * 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 nsDOMBlobBuilder_h
-#define nsDOMBlobBuilder_h
+#ifndef mozilla_dom_MultipartFileImpl_h
+#define mozilla_dom_MultipartFileImpl_h
 
 #include "mozilla/Attributes.h"
 #include "mozilla/CheckedInt.h"
@@ -120,79 +120,4 @@ protected:
   bool mIsFromNsIFile;
 };
 
-class BlobSet {
-public:
-  BlobSet()
-    : mData(nullptr), mDataLen(0), mDataBufferLen(0)
-  {}
-
-  ~BlobSet()
-  {
-    moz_free(mData);
-  }
-
-  nsresult AppendVoidPtr(const void* aData, uint32_t aLength);
-  nsresult AppendString(const nsAString& aString, bool nativeEOL, JSContext* aCx);
-  nsresult AppendBlobImpl(FileImpl* aBlobImpl);
-  nsresult AppendBlobImpls(const nsTArray<nsRefPtr<FileImpl>>& aBlobImpls);
-
-  nsTArray<nsRefPtr<FileImpl>>& GetBlobImpls() { Flush(); return mBlobImpls; }
-
-  already_AddRefed<File>
-  GetBlobInternal(nsISupports* aParent, const nsACString& aContentType)
-  {
-    nsRefPtr<File> blob = new File(aParent,
-      new MultipartFileImpl(GetBlobImpls(), NS_ConvertASCIItoUTF16(aContentType)));
-    return blob.forget();
-  }
-
-protected:
-  bool ExpandBufferSize(uint64_t aSize)
-  {
-    using mozilla::CheckedUint32;
-
-    if (mDataBufferLen >= mDataLen + aSize) {
-      mDataLen += aSize;
-      return true;
-    }
-
-    // Start at 1 or we'll loop forever.
-    CheckedUint32 bufferLen =
-      std::max<uint32_t>(static_cast<uint32_t>(mDataBufferLen), 1);
-    while (bufferLen.isValid() && bufferLen.value() < mDataLen + aSize)
-      bufferLen *= 2;
-
-    if (!bufferLen.isValid())
-      return false;
-
-    void* data = moz_realloc(mData, bufferLen.value());
-    if (!data)
-      return false;
-
-    mData = data;
-    mDataBufferLen = bufferLen.value();
-    mDataLen += aSize;
-    return true;
-  }
-
-  void Flush() {
-    if (mData) {
-      // If we have some data, create a blob for it
-      // and put it on the stack
-
-      nsRefPtr<FileImpl> blobImpl =
-        new FileImplMemory(mData, mDataLen, EmptyString());
-      mBlobImpls.AppendElement(blobImpl);
-      mData = nullptr; // The FileImplMemory takes ownership of the buffer
-      mDataLen = 0;
-      mDataBufferLen = 0;
-    }
-  }
-
-  nsTArray<nsRefPtr<FileImpl>> mBlobImpls;
-  void* mData;
-  uint64_t mDataLen;
-  uint64_t mDataBufferLen;
-};
-
-#endif
+#endif // mozilla_dom_MultipartFileImpl_h
diff --git a/content/base/src/moz.build b/content/base/src/moz.build
index c9ac5f42647b..358794428dac 100644
--- a/content/base/src/moz.build
+++ b/content/base/src/moz.build
@@ -104,6 +104,7 @@ UNIFIED_SOURCES += [
     'FragmentOrElement.cpp',
     'ImportManager.cpp',
     'Link.cpp',
+    'MultipartFileImpl.cpp',
     'NodeIterator.cpp',
     'nsAtomListUtils.cpp',
     'nsAttrAndChildArray.cpp',
@@ -125,7 +126,6 @@ UNIFIED_SOURCES += [
     'nsDataDocumentContentPolicy.cpp',
     'nsDocumentEncoder.cpp',
     'nsDOMAttributeMap.cpp',
-    'nsDOMBlobBuilder.cpp',
     'nsDOMCaretPosition.cpp',
     'nsDOMFileReader.cpp',
     'nsDOMMutationObserver.cpp',
diff --git a/content/base/src/nsXMLHttpRequest.cpp b/content/base/src/nsXMLHttpRequest.cpp
index 59b48e51cc43..108d8fa75b60 100644
--- a/content/base/src/nsXMLHttpRequest.cpp
+++ b/content/base/src/nsXMLHttpRequest.cpp
@@ -10,13 +10,13 @@
 #include <unistd.h>
 #endif
 #include "mozilla/ArrayUtils.h"
+#include "mozilla/dom/BlobSet.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/XMLHttpRequestUploadBinding.h"
 #include "mozilla/EventDispatcher.h"
 #include "mozilla/EventListenerManager.h"
 #include "mozilla/LoadInfo.h"
 #include "mozilla/MemoryReporting.h"
-#include "nsDOMBlobBuilder.h"
 #include "nsIDOMDocument.h"
 #include "mozilla/dom/ProgressEvent.h"
 #include "nsIJARChannel.h"
diff --git a/content/base/src/nsXMLHttpRequest.h b/content/base/src/nsXMLHttpRequest.h
index 36c6c8df9d11..f92747a70c6e 100644
--- a/content/base/src/nsXMLHttpRequest.h
+++ b/content/base/src/nsXMLHttpRequest.h
@@ -41,7 +41,6 @@
 #endif
 
 class AsyncVerifyRedirectCallbackForwarder;
-class BlobSet;
 class nsFormData;
 class nsIJARChannel;
 class nsILoadGroup;
@@ -51,6 +50,7 @@ class nsIJSID;
 namespace mozilla {
 
 namespace dom {
+class BlobSet;
 class File;
 }
 
@@ -676,7 +676,7 @@ protected:
   nsRefPtr<mozilla::dom::File> mDOMFile;
   // We stream data to mBlobSet when response type is "blob" or "moz-blob"
   // and mDOMFile is null.
-  nsAutoPtr<BlobSet> mBlobSet;
+  nsAutoPtr<mozilla::dom::BlobSet> mBlobSet;
 
   nsString mOverrideMimeType;
 
diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index 473631e36862..c3fe0c58dd49 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -35,7 +35,6 @@
 #include "nsIXPConnect.h"
 #include "xptcall.h"
 #include "nsTArray.h"
-#include "nsDOMBlobBuilder.h"
 
 // General helper includes
 #include "nsGlobalWindow.h"
diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index 22cdecc27c17..eecfba00a59b 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -74,7 +74,6 @@
 #include "mozilla/dom/PermissionMessageUtils.h"
 #include "mozilla/dom/quota/PersistenceType.h"
 #include "mozilla/dom/quota/QuotaManager.h"
-#include "nsDOMBlobBuilder.h"
 #include "nsPrintfCString.h"
 #include "nsViewportInfo.h"
 #include "nsIFormControl.h"
diff --git a/dom/devicestorage/nsDeviceStorage.cpp b/dom/devicestorage/nsDeviceStorage.cpp
index fac8f1b8457b..f51ebee2d687 100644
--- a/dom/devicestorage/nsDeviceStorage.cpp
+++ b/dom/devicestorage/nsDeviceStorage.cpp
@@ -36,7 +36,6 @@
 #include "nsIDirectoryEnumerator.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "nsDirectoryServiceDefs.h"
-#include "nsDOMBlobBuilder.h"
 #include "nsNetUtil.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsIPrincipal.h"
diff --git a/js/xpconnect/loader/mozJSComponentLoader.cpp b/js/xpconnect/loader/mozJSComponentLoader.cpp
index bb058b429cba..31f87c2f1097 100644
--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -34,7 +34,6 @@
 #include "nsIFileURL.h"
 #include "nsIJARURI.h"
 #include "nsNetUtil.h"
-#include "nsDOMBlobBuilder.h"
 #include "jsprf.h"
 #include "nsJSPrincipals.h"
 #include "nsJSUtils.h"
diff --git a/layout/build/nsLayoutModule.cpp b/layout/build/nsLayoutModule.cpp
index 39572d36fc09..b5752093f264 100644
--- a/layout/build/nsLayoutModule.cpp
+++ b/layout/build/nsLayoutModule.cpp
@@ -67,7 +67,6 @@
 #include "nsContentCreatorFunctions.h"
 
 // DOM includes
-#include "nsDOMBlobBuilder.h"
 #include "nsDOMFileReader.h"
 
 #include "nsFormData.h"