Add UMA to HTMLCanvasElement to track image formats usage of toDataURL/toBlob

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.h b/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
index e7bb8bbb4369218d4e700e60f7e7d6304a717fc2..72ee12061f611bde006a903471c80b165f242cc5 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
@@ -98,7 +98,7 @@ public:
 
     bool isPaintable() const;
 
-    static String toEncodingMimeType(const String& mimeType);
+    static String toEncodingMimeType(const String& mimeType, const String& callFunctionName);
     String toDataURL(const String& mimeType, const ScriptValue& qualityArgument, ExceptionState&) const;
     String toDataURL(const String& mimeType, ExceptionState& exceptionState) const { return toDataURL(mimeType, ScriptValue(), exceptionState); }
 
@@ -185,6 +185,17 @@ public:
     bool isSupportedInteractiveCanvasFallback(const Element&);
     std::pair<Element*, String> getControlAndIdIfHitRegionExists(const LayoutPoint&);
 
+    enum CanvasReturnImageFormat {

[Justin Novosad, 2016/03/22 15:09:04]

This does not need to be in the header. Also, why "CanvasReturn"?  IMHO, a mor
appropriate name would be "RequestedImageMimeType"

+        Png = 0,

[Justin Novosad, 2016/03/22 15:09:04]

enum members should have the enum name as a prefix. Something like
RequestedImageMimeTypeJpeg

+        Jpeg = 1,
+        Webp = 2,
+        Gif = 3,
+        Bmp = 4,
+        Ico = 5,
+        Tiff = 6,
+        NumberOfImageFormats

[Justin Novosad, 2016/03/22 15:09:04]

You should add an "Unknown" value

+    };
+
 protected:
     void didMoveToNewDocument(Document& oldDocument) override;