GIF Animations "clear from cache related glitch" fix

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp

Index: third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp
index b660c660eb881bd73c788b7b7b1f43c765f20169..60b423a93182ca701f349c116c4708e9e5c16066 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp
@@ -194,6 +194,22 @@ size_t ImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame)
     return frameBytesCleared;
 }
 
+size_t ImageDecoder::clearCacheExceptFrames(const SizeTHashSet& clearExceptFrames)
+{
+    // Don't clear if there are no frames or only one frame.

[tomhudson, 2016/01/12 16:15:59]

This comment is backwards. It's nearly obvious from the following two lines of
code that you aren't clearing if there are 0 or 1 frames, but it's completely
inobvious *WHY*.

[aleksandar.stojiljkovic, 2016/01/12 17:34:59]

Done.

+    if (m_frameBufferCache.size() <= 1)
+        return 0;
+
+    size_t frameBytesCleared = 0;
+    for (size_t i = 0; i < m_frameBufferCache.size(); ++i) {
+        if (m_frameBufferCache[i].status() != ImageFrame::FrameEmpty && !clearExceptFrames.contains(i)) {
+            frameBytesCleared += frameBytesAtIndex(i);
+            clearFrameBuffer(i);
+        }
+    }
+    return frameBytesCleared;
+}
+
 void ImageDecoder::clearFrameBuffer(size_t frameIndex)
 {
     m_frameBufferCache[frameIndex].clearPixelData();