Add animation support for WebP images

Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp

Index: Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
diff --git a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
index 2b5603b00cd4a02cefcc6cf131cfd959c9903aff..28b2f823d94398f2e8929dd06ea7d570db9134c4 100644
--- a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
+++ b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
@@ -305,13 +305,8 @@ void GIFImageDecoder::decode(size_t frameIndex)
         frameToDecode = m_frameBufferCache[frameToDecode].requiredPreviousFrameIndex();
     } while (frameToDecode != notFound && m_frameBufferCache[frameToDecode].status() != ImageFrame::FrameComplete);
 
-    // The |rend| variable is needed by some compilers that can't correctly
-    // select from const and non-const versions of overloaded functions.
-    // Can remove the variable if Android compiler can compile
-    // 'iter != framesToDecode.rend()'.
-    Vector<size_t>::const_reverse_iterator rend = framesToDecode.rend();
-    for (Vector<size_t>::const_reverse_iterator iter = framesToDecode.rbegin(); iter != rend; ++iter) {
-        size_t frameIndex = *iter;
+    for (size_t i = framesToDecode.size(); i > 0; --i) {
+        size_t frameIndex = framesToDecode[i - 1];
         if (!m_reader->decode(frameIndex)) {
             setFailed();
             return;