Implement Asynchronous image encoding for Canvas.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 7173957a4058858e351c7dfdc0b3cc0cc92042ce..aab36f860151615d00b3cf8ca0d25254bc9dd7c4 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
@@ -31,6 +31,7 @@
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/UnionTypesCore.h"
 #include "core/CoreExport.h"
+#include "core/dom/DOMTypedArray.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentVisibilityObserver.h"
 #include "core/fileapi/FileCallback.h"
@@ -42,6 +43,7 @@
 #include "platform/graphics/GraphicsTypes3D.h"
 #include "platform/graphics/ImageBufferClient.h"
 #include "platform/heap/Handle.h"
+#include "public/platform/WebThread.h"
 
 #define CanvasDefaultInterpolationQuality InterpolationLow
 
@@ -78,6 +80,9 @@ public:
     DECLARE_NODE_FACTORY(HTMLCanvasElement);
     ~HTMLCanvasElement() override;
 
+    static PassOwnPtr<WebThread> getToBlobThreadInstance();

[Justin Novosad, 2015/09/24 20:51:31]

This is not a proper use of PassOwnPtr. I really think that wrapping the thread
ownership in a singleton would be the way to go here. I looked through blink
code, and I found one really clean example of a singleton that owns a thread,
with explicit initialization and teardown, which is nice because it means we are
not even leaking the singleton. Checkout CompositorWorkerManager. In your case,
you are not in a module, so your global init/uninit would go in WebKit.cpp 

+    static int s_numCanvasInstances; 
+
     void addObserver(CanvasObserver*);
     void removeObserver(CanvasObserver*);
 
@@ -114,7 +119,7 @@ public:
     String toDataURL(const String& mimeType, const ScriptValue& qualityArgument, ExceptionState&) const;
     String toDataURL(const String& mimeType, ExceptionState& exceptionState) const { return toDataURL(mimeType, ScriptValue(), exceptionState); }
 
-    void toBlob(FileCallback*, const String& mimeType, const ScriptValue& qualityArgument, ExceptionState&) const;
+    void toBlob(FileCallback*, const String& mimeType, const ScriptValue& qualityArgument, ExceptionState&);
     void toBlob(FileCallback* callback, const String& mimeType, ExceptionState& exceptionState) { return toBlob(callback, mimeType, ScriptValue(), exceptionState); }
 
     // Used for rendering
@@ -209,7 +214,10 @@ private:
     bool paintsIntoCanvasBuffer() const;
 
     ImageData* toImageData(SourceDrawingBuffer) const;
-    String toDataURLInternal(const String& mimeType, const double* quality, SourceDrawingBuffer) const;
+    String toDataURLInternal(const String& mimeType, const double& quality, SourceDrawingBuffer) const;
+
+    void encodeImageAsync(DOMUint8ClampedArray* imagedata, IntSize imageSize, FileCallback*, const String& mimeType, double quality);
+    void createBlobAndCall(PassOwnPtr<Vector<char>> encodedImage, const String& mimeType, FileCallback*);
 
     WillBeHeapHashSet<RawPtrWillBeWeakMember<CanvasObserver>> m_observers;