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..fa618ae49bfe0fce70a699d6f2c2fb998e5c97d4 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -492,14 +492,54 @@ void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
     }
 }
 
-String HTMLCanvasElement::toEncodingMimeType(const String& mimeType)
+enum RequestedImageMimeType {

[jwd, 2016/03/23 19:05:12]

Can you add a comment that this enum is used for a histogram, and the values
should not be changed.

+    RequestedImageMimeTypePng = 0,
+    RequestedImageMimeTypeJpeg = 1,
+    RequestedImageMimeTypeWebp = 2,
+    RequestedImageMimeTypeGif = 3,
+    RequestedImageMimeTypeBmp = 4,
+    RequestedImageMimeTypeIco = 5,
+    RequestedImageMimeTypeTiff = 6,
+    RequestedImageMimeTypeUnknown = 7,
+    NumberOfRequestedImageMimeTypes
+};
+
+String HTMLCanvasElement::toEncodingMimeType(const String& mimeType, const EncodeReason encodeReason)
 {
     String lowercaseMimeType = mimeType.lower();
+    if (mimeType.isNull())
+        lowercaseMimeType = DefaultMimeType;
+
+    RequestedImageMimeType imageFormat;
+    if (lowercaseMimeType == "image/png") {
+        imageFormat = RequestedImageMimeTypePng;
+    } else if (lowercaseMimeType == "image/jpeg") {
+        imageFormat = RequestedImageMimeTypeJpeg;
+    } else if (lowercaseMimeType == "image/webp") {
+        imageFormat = RequestedImageMimeTypeWebp;
+    } else if (lowercaseMimeType == "image/gif") {
+        imageFormat = RequestedImageMimeTypeGif;
+    } else if (lowercaseMimeType == "image/bmp" || lowercaseMimeType == "image/x-windows-bmp") {
+        imageFormat = RequestedImageMimeTypeBmp;
+    } else if (lowercaseMimeType == "image/x-icon") {
+        imageFormat = RequestedImageMimeTypeIco;
+    } else if (lowercaseMimeType == "image/tiff" || lowercaseMimeType == "image/x-tiff") {
+        imageFormat = RequestedImageMimeTypeTiff;
+    } else {
+        imageFormat = RequestedImageMimeTypeUnknown;
+    }
+
+    if (encodeReason == EncodeReasonToDataURL) {
+        DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, toDataURLImageFormatHistogram, new EnumerationHistogram("Canvas.RequestedImageMimeTypes_toDataURL", NumberOfRequestedImageMimeTypes));

[Justin Novosad, 2016/03/23 19:35:48]

Are you sure it is correct to use "_" as the suffix separator? I thought we used
"."

+        toDataURLImageFormatHistogram.count(imageFormat);
+    } else if (encodeReason == EncodeReasonToBlobCallback) {
+        DEFINE_THREAD_SAFE_STATIC_LOCAL(EnumerationHistogram, toBlobCallbackImageFormatHistogram, new EnumerationHistogram("Canvas.RequestedImageMimeTypes_toBlobCallback", NumberOfRequestedImageMimeTypes));
+        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 +594,7 @@ String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double
     if (!isPaintable())
         return String("data:,");
 
-    String encodingMimeType = toEncodingMimeType(mimeType);
+    String encodingMimeType = toEncodingMimeType(mimeType, EncodeReasonToDataURL);
 
     ImageData* imageData = toImageData(sourceBuffer, SnapshotReasonToDataURL);
     ScopedDisposal<ImageData> disposer(imageData);
@@ -599,7 +639,7 @@ void HTMLCanvasElement::toBlob(BlobCallback* callback, const String& mimeType, c
         }
     }
 
-    String encodingMimeType = toEncodingMimeType(mimeType);
+    String encodingMimeType = toEncodingMimeType(mimeType, EncodeReasonToBlobCallback);
 
     ImageData* imageData = toImageData(BackBuffer, SnapshotReasonToBlob);
     // imageData unref its data, which we still keep alive for the async toBlob thread