Record UMA stats for Blink decoded image types

Source/platform/image-decoders/gif/GIFImageDecoder.h

Index: Source/platform/image-decoders/gif/GIFImageDecoder.h
diff --git a/Source/platform/image-decoders/gif/GIFImageDecoder.h b/Source/platform/image-decoders/gif/GIFImageDecoder.h
index ed2f6ce313953e72ec5f326f6ee56abe930cab26..ea4049be6913778cf15db7efc2d0be9a030867d8 100644
--- a/Source/platform/image-decoders/gif/GIFImageDecoder.h
+++ b/Source/platform/image-decoders/gif/GIFImageDecoder.h
@@ -67,7 +67,11 @@ public:
 private:
     // ImageDecoder:
     void clearFrameBuffer(size_t frameIndex) override;
-    virtual void decodeSize() { parse(GIFSizeQuery); }
+    virtual void decodeSize()
+    {
+        parse(GIFSizeQuery);
+        reportStats(ImageGIF);
+    }
     size_t decodeFrameCount() override;
     void initializeNewFrame(size_t) override;
     void decode(size_t) override;