Track positions of dimensions in image files

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp

Index: third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp
index 4c6631dfe2b4ea139902f443fdf716cde83a9c68..727bcf12513958e19467d3fd1843017c11c5b92e 100644
--- a/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/gif/GIFImageReader.cpp
@@ -463,7 +463,7 @@ bool GIFImageReader::parseData(size_t dataPosition, size_t len, GIFImageDecoder:
             // change after we read the first frame's image header.
             m_screenWidth = GETINT16(currentComponent);
             m_screenHeight = GETINT16(currentComponent + 2);
-
+            m_client->setSizeOffsetOptimized(currentComponentPosition + 4);
             const size_t globalColorMapColors = 2 << (currentComponent[4] & 0x07);
 
             if ((currentComponent[4] & 0x80) && globalColorMapColors > 0) { /* global map */
@@ -689,6 +689,10 @@ bool GIFImageReader::parseData(size_t dataPosition, size_t len, GIFImageDecoder:
             // set to zero, since usually the first frame completely fills
             // the image.
             if (currentFrameIsFirstFrame()) {
+                bool updated = (m_screenHeight < yOffset + height || m_screenWidth < yOffset + width);
+                if (updated)
+                    m_client->setSizeOffsetOptimized(0);
+                m_client->setSizeOffset(currentComponentPosition + 8);
                 m_screenHeight = std::max(m_screenHeight, yOffset + height);
                 m_screenWidth = std::max(m_screenWidth, xOffset + width);
             }