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

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

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 474 matching lines @@
 {
     m_size = size;
     m_didFailToCreateImageBuffer = false;
     discardImageBuffer();
     clearCopiedImage();
     if (m_context && m_context->is2d() && m_context->isContextLost()) {
         m_context->didSetSurfaceSize();
     }
 }
 
-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;
 }
 
 const AtomicString HTMLCanvasElement::imageSourceURL() const
 {
     return AtomicString(toDataURLInternal(DefaultMimeType, 0, FrontBuffer));
 }
 
 void HTMLCanvasElement::prepareSurfaceForPaintingIfNeeded() const
 {
@@ skipping 34 matching lines @@
     }
 
     return imageData;
 }
 
 String HTMLCanvasElement::toDataURLInternal(const String& mimeType, const double& quality, SourceDrawingBuffer sourceBuffer) const
 {
     if (!isPaintable())
         return String("data:,");
 
-    String encodingMimeType = toEncodingMimeType(mimeType);
+    String encodingMimeType = toEncodingMimeType(mimeType, EncodeReasonToDataURL);
 
     ImageData* imageData = toImageData(sourceBuffer, SnapshotReasonToDataURL);
     ScopedDisposal<ImageData> disposer(imageData);
 
     return ImageDataBuffer(imageData->size(), imageData->data()->data()).toDataURL(encodingMimeType, quality);
 }
 
 String HTMLCanvasElement::toDataURL(const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState) const
 {
     if (!originClean()) {
@@ skipping 24 matching lines @@
     }
 
     double quality = UndefinedQualityValue;
     if (!qualityArgument.isEmpty()) {
         v8::Local<v8::Value> v8Value = qualityArgument.v8Value();
         if (v8Value->IsNumber()) {
             quality = v8Value.As<v8::Number>()->Value();
         }
     }
 
-    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
     ScopedDisposal<ImageData> disposer(imageData);
     // Add a ref to keep image data alive until completion of encoding
     RefPtr<DOMUint8ClampedArray> imageDataRef(imageData->data());
 
     RefPtr<CanvasAsyncBlobCreator> asyncCreatorRef = CanvasAsyncBlobCreator::create(imageDataRef.release(), encodingMimeType, imageData->size(), callback);
 
     if (encodingMimeType == DefaultMimeType) {
@@ skipping 467 matching lines @@
 }
 
 std::pair<Element*, String> HTMLCanvasElement::getControlAndIdIfHitRegionExists(const LayoutPoint& location)
 {
     if (m_context && m_context->is2d())
         return m_context->getControlAndIdIfHitRegionExists(location);
     return std::make_pair(nullptr, String());
 }
 
 } // namespace blink