Do not clear canvas with transparent color after creating SkSurface

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 114 matching lines @@
         return false;
     if (size.width() > MaxSkiaDim || size.height() > MaxSkiaDim)
         return false;
     return true;
 }
 
 PassRefPtr<Image> createTransparentImage(const IntSize& size)
 {
     DCHECK(canCreateImageBuffer(size));
     sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(size.width(), size.height());
-    surface->getCanvas()->clear(SK_ColorTRANSPARENT);
     return StaticBitmapImage::create(fromSkSp(surface->makeImageSnapshot()));
 }
 
 } // namespace
 
 inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     : HTMLElement(canvasTag, document)
     , ContextLifecycleObserver(&document)
     , PageLifecycleObserver(document.page())
     , m_size(DefaultWidth, DefaultHeight)
@@ skipping 1041 matching lines @@
 
 bool HTMLCanvasElement::createSurfaceLayer()
 {
     DCHECK(!m_surfaceLayerBridge);
     std::unique_ptr<CanvasSurfaceLayerBridgeClient> bridgeClient = wrapUnique(new CanvasSurfaceLayerBridgeClientImpl());
     m_surfaceLayerBridge = wrapUnique(new CanvasSurfaceLayerBridge(std::move(bridgeClient)));
     return m_surfaceLayerBridge->createSurfaceLayer(this->width(), this->height());
 }
 
 } // namespace blink