Decode GIF image frames on demand.

Source/core/platform/graphics/BitmapImage.cpp

Index: Source/core/platform/graphics/BitmapImage.cpp
diff --git a/Source/core/platform/graphics/BitmapImage.cpp b/Source/core/platform/graphics/BitmapImage.cpp
index 1f34b02046832703e60588312b9cf1b652080329..1f98323fb1aa961ac8b13f4e74ce6000d94a3999 100644
--- a/Source/core/platform/graphics/BitmapImage.cpp
+++ b/Source/core/platform/graphics/BitmapImage.cpp
@@ -84,12 +84,10 @@ bool BitmapImage::hasSingleSecurityOrigin() const
 void BitmapImage::destroyDecodedData(bool destroyAll)
 {
     unsigned frameBytesCleared = 0;
-    const size_t clearBeforeFrame = destroyAll ? m_frames.size() : m_currentFrame;
+    for (size_t i = 0; i < m_frames.size(); ++i) {
+        if (!destroyAll && i == m_currentFrame)
+            continue;
 
-    // Because we can advance frames without always needing to decode the actual
-    // bitmap data, |m_currentFrame| may be larger than m_frames.size();
-    // make sure not to walk off the end of the container in this case.
-    for (size_t i = 0; i < std::min(clearBeforeFrame, m_frames.size()); ++i) {
         // The underlying frame isn't actually changing (we're just trying to
         // save the memory for the framebuffer data), so we don't need to clear
         // the metadata.
@@ -100,7 +98,7 @@ void BitmapImage::destroyDecodedData(bool destroyAll)
 
     destroyMetadataAndNotify(frameBytesCleared);
 
-    m_source.clear(destroyAll, clearBeforeFrame, data(), m_allDataReceived);
+    m_source.clear(destroyAll, m_currentFrame, data(), m_allDataReceived);
     return;
 }
 
@@ -532,7 +530,6 @@ bool BitmapImage::internalAdvanceAnimation(bool skippingFrames)
 
     ++m_currentFrame;
     bool advancedAnimation = true;
-    bool destroyAll = false;
     if (m_currentFrame >= frameCount()) {
         ++m_repetitionsComplete;
 
@@ -546,12 +543,10 @@ bool BitmapImage::internalAdvanceAnimation(bool skippingFrames)
             m_desiredFrameStartTime = 0;
             --m_currentFrame;
             advancedAnimation = false;
-        } else {
+        } else
             m_currentFrame = 0;
-            destroyAll = true;
-        }
     }
-    destroyDecodedDataIfNecessary(destroyAll);
+    destroyDecodedDataIfNecessary(false);
 
     // We need to draw this frame if we advanced to it while not skipping, or if
     // while trying to skip frames we hit the last frame and thus had to stop.