Revert of Simplify CanvasAsyncBlobCreator by removing ContextObserver and related tests

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 562 matching lines @@
     double quality = UndefinedQualityValue;
     if (!qualityArgument.isEmpty()) {
         v8::Local<v8::Value> v8Value = qualityArgument.v8Value();
         if (v8Value->IsNumber()) {
             quality = v8Value.As<v8::Number>()->Value();
         }
     }
     return toDataURLInternal(mimeType, quality, BackBuffer);
 }
 
-void HTMLCanvasElement::toBlob(BlobCallback* callback, const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState)
+void HTMLCanvasElement::toBlob(ScriptState* scriptState, BlobCallback* callback, const String& mimeType, const ScriptValue& qualityArgument, ExceptionState& exceptionState)
 {
     if (!originClean()) {
         exceptionState.throwSecurityError("Tainted canvases may not be exported.");
         return;
     }
 
     if (!isPaintable()) {
         // If the canvas element's bitmap has no pixels
         Platform::current()->mainThread()->taskRunner()->postTask(BLINK_FROM_HERE, bind(&BlobCallback::handleEvent, callback, nullptr));
         return;
     }
 
     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);
 
     ImageData* imageData = toImageData(BackBuffer);
     // 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);
+    RefPtr<CanvasAsyncBlobCreator> asyncCreatorRef = CanvasAsyncBlobCreator::create(imageDataRef.release(), encodingMimeType, imageData->size(), callback, scriptState->executionContext());
 
-    if (encodingMimeType == DefaultMimeType) {
+    if (Platform::current()->isThreadedCompositingEnabled() && (encodingMimeType == DefaultMimeType)) {
         asyncCreatorRef->scheduleAsyncBlobCreation(true);
     } else {
         asyncCreatorRef->scheduleAsyncBlobCreation(false, quality);
     }
 }
 
 void HTMLCanvasElement::addListener(CanvasDrawListener* listener)
 {
     m_listeners.add(listener);
 }
@@ skipping 391 matching lines @@
     }
     return ImageBitmapSource::fulfillImageBitmap(scriptState, isPaintable() ? ImageBitmap::create(this, IntRect(sx, sy, sw, sh), options) : nullptr);
 }
 
 bool HTMLCanvasElement::isOpaque() const
 {
     return m_context && !m_context->hasAlpha();
 }
 
 } // namespace blink