Change Canvas2DLayerBridge to stay alive until last mailbox is returned.

Source/core/platform/graphics/ImageBuffer.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
@@ skipping 44 matching lines @@
 #include "third_party/skia/include/gpu/GrContext.h"
 #include "third_party/skia/include/gpu/SkGpuDevice.h"
 #include "wtf/MathExtras.h"
 #include "wtf/text/Base64.h"
 #include "wtf/text/WTFString.h"
 
 using namespace std;
 
 namespace WebCore {
 
-static SkCanvas* createAcceleratedCanvas(const IntSize& size, OwnPtr<Canvas2DLayerBridge>* outLayerBridge, OpacityMode opacityMode)
+static SkCanvas* createAcceleratedCanvas(const IntSize& size, Canvas2DLayerBridgePtr* outLayerBridge, OpacityMode opacityMode)
 {
     RefPtr<GraphicsContext3D> context3D = SharedGraphicsContext3D::get();
     if (!context3D)
         return 0;
     Canvas2DLayerBridge::OpacityMode bridgeOpacityMode = opacityMode == Opaque ? Canvas2DLayerBridge::Opaque : Canvas2DLayerBridge::NonOpaque;
     *outLayerBridge = Canvas2DLayerBridge::create(context3D.release(), size, bridgeOpacityMode);
     // If canvas buffer allocation failed, debug build will have asserted
     // For release builds, we must verify whether the device has a render target
     return (*outLayerBridge) ? (*outLayerBridge)->getCanvas() : 0;
 }
@@ skipping 92 matching lines @@
         // We're using context acquisition as a signal that someone is about to render into our buffer and we need
         // to be ready. This isn't logically const-correct, hence the cast.
         const_cast<Canvas2DLayerBridge*>(m_layerBridge.get())->contextAcquired();
     }
     return m_context.get();
 }
 
 
 bool ImageBuffer::isValid() const
 {
-    if (m_layerBridge.get())
+    if (m_layerBridge)
         return const_cast<Canvas2DLayerBridge*>(m_layerBridge.get())->isValid();
     return true;
 }
 
 static SkBitmap deepSkBitmapCopy(const SkBitmap& bitmap)
 {
     SkBitmap tmp;
     if (!bitmap.deepCopyTo(&tmp, bitmap.config()))
         bitmap.copyTo(&tmp, bitmap.config());
 
@@ skipping 301 matching lines @@
     if (!encodeImage(imageData, mimeType, quality, &encodedImage))
         return "data:,";
 
     Vector<char> base64Data;
     base64Encode(encodedImage, base64Data);
 
     return "data:" + mimeType + ";base64," + base64Data;
 }
 
 } // namespace WebCore