diff -r 000000000000 -r 6474c204b198 image/src/FrameSequence.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/image/src/FrameSequence.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,106 @@
+/* -*- 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/. */
+
+#include "FrameSequence.h"
+
+using namespace mozilla;
+using namespace mozilla::image;
+
+namespace mozilla {
+namespace image {
+
+FrameSequence::~FrameSequence()
+{
+  ClearFrames();
+}
+
+const FrameDataPair&
+FrameSequence::GetFrame(uint32_t framenum) const
+{
+  if (framenum >= mFrames.Length()) {
+    static FrameDataPair empty;
+    return empty;
+  }
+
+  return mFrames[framenum];
+}
+
+uint32_t
+FrameSequence::GetNumFrames() const
+{
+  return mFrames.Length();
+}
+
+void
+FrameSequence::RemoveFrame(uint32_t framenum)
+{
+  NS_ABORT_IF_FALSE(framenum < mFrames.Length(), "Deleting invalid frame!");
+
+  mFrames.RemoveElementAt(framenum);
+}
+
+void
+FrameSequence::ClearFrames()
+{
+  // Since FrameDataPair holds an nsAutoPtr to its frame, clearing the mFrames
+  // array also deletes all the frames.
+  mFrames.Clear();
+}
+
+void
+FrameSequence::InsertFrame(uint32_t framenum, imgFrame* aFrame)
+{
+  NS_ABORT_IF_FALSE(framenum <= mFrames.Length(), "Inserting invalid frame!");
+  mFrames.InsertElementAt(framenum, aFrame);
+  if (GetNumFrames() > 1) {
+    // If we're creating our second element, we now know we're animated.
+    // Therefore, we need to lock the first frame too.
+    if (GetNumFrames() == 2) {
+      mFrames[0].LockAndGetData();
+    }
+
+    // Whenever we have more than one frame, we always lock *all* our frames
+    // so we have all the image data pointers.
+    mFrames[framenum].LockAndGetData();
+  }
+}
+
+imgFrame*
+FrameSequence::SwapFrame(uint32_t framenum, imgFrame* aFrame)
+{
+  NS_ABORT_IF_FALSE(framenum < mFrames.Length(), "Swapping invalid frame!");
+
+  FrameDataPair ret;
+
+  // Steal the imgFrame.
+  if (framenum < mFrames.Length()) {
+    ret = mFrames[framenum];
+  }
+
+  if (aFrame) {
+    mFrames.ReplaceElementAt(framenum, aFrame);
+  } else {
+    mFrames.RemoveElementAt(framenum);
+  }
+
+  return ret.Forget();
+}
+
+size_t
+FrameSequence::SizeOfDecodedWithComputedFallbackIfHeap(gfxMemoryLocation aLocation,
+                                                       MallocSizeOf aMallocSizeOf) const
+{
+  size_t n = 0;
+  for (uint32_t i = 0; i < mFrames.Length(); ++i) {
+    imgFrame* frame = mFrames.SafeElementAt(i, FrameDataPair());
+    NS_ABORT_IF_FALSE(frame, "Null frame in frame array!");
+    n += frame->SizeOfExcludingThisWithComputedFallbackIfHeap(aLocation, aMallocSizeOf);
+  }
+
+  return n;
+}
+
+} // namespace image
+} // namespace mozilla