canvas: make a temporary buffer when a context doesn't exist.

Source/core/frame/ImageBitmap.cpp

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/frame/ImageBitmap.h"
 
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLVideoElement.h"
 #include "core/html/ImageData.h"
-#include "core/html/canvas/CanvasRenderingContext.h"
 #include "platform/graphics/BitmapImage.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/ImageBuffer.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 static inline IntRect normalizeRect(const IntRect& rect)
 {
     return IntRect(std::min(rect.x(), rect.maxX()),
@@ skipping 51 matching lines @@
     video->paintCurrentFrameInContext(c, videoRect);
     m_bitmap = buf->copyImage(DontCopyBackingStore);
     m_bitmapRect = IntRect(IntPoint(std::max(0, -cropRect.x()), std::max(0, -cropRect.y())), srcRect.size());
 }
 
 ImageBitmap::ImageBitmap(HTMLCanvasElement* canvas, const IntRect& cropRect)
     : m_imageElement(nullptr)
     , m_cropRect(cropRect)
     , m_bitmapOffset(IntPoint())
 {
-    CanvasRenderingContext* sourceContext = canvas->renderingContext();
-    if (sourceContext && sourceContext->is3d())
-        sourceContext->paintRenderingResultsToCanvas(BackBuffer);
-
     IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), canvas->size()));
     m_bitmapRect = IntRect(IntPoint(std::max(0, -cropRect.x()), std::max(0, -cropRect.y())), srcRect.size());
-    m_bitmap = cropImage(canvas->buffer()->copyImage(CopyBackingStore).get(), cropRect);
+    ASSERT(canvas->isPaintable());
+    m_bitmap = cropImage(canvas->copiedImage(BackBuffer).get(), cropRect);
 }
 
 ImageBitmap::ImageBitmap(ImageData* data, const IntRect& cropRect)
     : m_imageElement(nullptr)
     , m_cropRect(cropRect)
     , m_bitmapOffset(IntPoint())
 {
     IntRect srcRect = intersection(cropRect, IntRect(IntPoint(), data->size()));
 
     OwnPtr<ImageBuffer> buf = ImageBuffer::create(data->size());
@@ skipping 117 matching lines @@
     return FloatSize(width(), height());
 }
 
 void ImageBitmap::trace(Visitor* visitor)
 {
     visitor->trace(m_imageElement);
     ImageLoaderClient::trace(visitor);
 }
 
 } // namespace blink