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

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

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index 80d196bcc1ba02d4519451fad4f66b009db6d91f..81ea8feeff2dce39c42e1255e1a24a77aacce6a6 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -492,14 +492,44 @@ void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
     }
 }
 
-String HTMLCanvasElement::toEncodingMimeType(const String& mimeType)
+String HTMLCanvasElement::toEncodingMimeType(const String& mimeType, const String& callFunctionName)
 {
     String lowercaseMimeType = mimeType.lower();
+    if (mimeType.isNull())
+        lowercaseMimeType = DefaultMimeType;
+
+    CanvasReturnImageFormat imageFormat;
+    if (lowercaseMimeType == "image/png") {
+        imageFormat = CanvasReturnImageFormat::Png;
+    } else if (lowercaseMimeType == "image/jpeg") {
+        imageFormat = CanvasReturnImageFormat::Jpeg;
+    } else if (lowercaseMimeType == "image/webp") {
+        imageFormat = CanvasReturnImageFormat::Webp;
+    } else if (lowercaseMimeType == "image/gif") {
+        imageFormat = CanvasReturnImageFormat::Gif;
+    } else if (lowercaseMimeType == "image/bmp") {

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

There is also an alternate MIME type for bmp: image/x-windows-bmp

+        imageFormat = CanvasReturnImageFormat::Bmp;
+    } else if (lowercaseMimeType == "image/ico") {

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

this is not a valid MIME type. should be "image/x-icon"

+        imageFormat = CanvasReturnImageFormat::Ico;
+    } else if (lowercaseMimeType == "image/tiff") {

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

can also be image/x-tiff

+        imageFormat = CanvasReturnImageFormat::Tiff;
+    } else {
+        imageFormat = CanvasReturnImageFormat::NumberOfImageFormats;
+    }
+
+    if (imageFormat != CanvasReturnImageFormat::NumberOfImageFormats) {
+        if (callFunctionName == "toDataURL") {
+            DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, toDataURLImageFormatHistogram, new EnumerationHistogram("Canvas.ReturnImageFormats.toDataURL", CanvasReturnImageFormat::NumberOfImageFormats));
+            toDataURLImageFormatHistogram.count(imageFormat);
+        } else if (callFunctionName == "toBlobCallback") {
+            DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, toBlobCallbackImageFormatHistogram, new EnumerationHistogram("Canvas.ReturnImageFormats.toBlobCallback", CanvasReturnImageFormat::NumberOfImageFormats));
+            toBlobCallbackImageFormatHistogram.count(imageFormat);
+        }
+    }
 
     // FIXME: Make isSupportedImageMIMETypeForEncoding threadsafe (to allow this method to be used on a worker thread).
-    if (mimeType.isNull() || !MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(lowercaseMimeType))
+    if (!MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(lowercaseMimeType))
         lowercaseMimeType = DefaultMimeType;
-
     return lowercaseMimeType;
 }
 
@@ -554,7 +584,7 @@ String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double
     if (!isPaintable())
         return String("data:,");
 
-    String encodingMimeType = toEncodingMimeType(mimeType);
+    String encodingMimeType = toEncodingMimeType(mimeType, "toDataURL");
 
     ImageData* imageData = toImageData(sourceBuffer, SnapshotReasonToDataURL);
     ScopedDisposal<ImageData> disposer(imageData);
@@ -599,7 +629,7 @@ void HTMLCanvasElement::toBlob(BlobCallback* callback, const String& mimeType, c
         }
     }
 
-    String encodingMimeType = toEncodingMimeType(mimeType);
+    String encodingMimeType = toEncodingMimeType(mimeType, "toBlobCallback");
 
     ImageData* imageData = toImageData(BackBuffer, SnapshotReasonToBlob);
     // imageData unref its data, which we still keep alive for the async toBlob thread