Allow fallbackFactory to be null in RecordingImageBufferSurface.

third_party/WebKit/Source/platform/graphics/RecordingImageBufferSurface.h

 // Copyright 2014 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.
 
 #ifndef RecordingImageBufferSurface_h
 #define RecordingImageBufferSurface_h
 
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/ImageBufferSurface.h"
 #include "public/platform/WebThread.h"
@@ skipping 17 matching lines @@
 public:
     virtual PassOwnPtr<ImageBufferSurface> createSurface(const IntSize&, OpacityMode) = 0;
     virtual ~RecordingImageBufferFallbackSurfaceFactory() { }
 protected:
     RecordingImageBufferFallbackSurfaceFactory() { }
 };
 
 class PLATFORM_EXPORT RecordingImageBufferSurface : public ImageBufferSurface {
     WTF_MAKE_NONCOPYABLE(RecordingImageBufferSurface); USING_FAST_MALLOC(RecordingImageBufferSurface);
 public:
-    RecordingImageBufferSurface(const IntSize&, PassOwnPtr<RecordingImageBufferFallbackSurfaceFactory> fallbackFactory, OpacityMode = NonOpaque);
+    // If the fallbackFactory is null the buffer surface should only be used
+    // for one frame and should not be used for any operations which need a
+    // raster surface, (i.e. writePixels).
+    // Only #getPicture should be used to access the resulting frame.
+    RecordingImageBufferSurface(const IntSize&, PassOwnPtr<RecordingImageBufferFallbackSurfaceFactory> fallbackFactory = nullptr, OpacityMode = NonOpaque);
     ~RecordingImageBufferSurface() override;
 
     // Implementation of ImageBufferSurface interfaces
     SkCanvas* canvas() override;
     void disableDeferral(DisableDeferralReason) override;
     PassRefPtr<SkPicture> getPicture() override;
     void flush(FlushReason) override;
     void didDraw(const FloatRect&) override;
     bool isValid() const override { return true; }
     bool isRecording() const override { return !m_fallbackSurface; }
@@ skipping 51 matching lines @@
     bool m_frameWasCleared;
     bool m_didRecordDrawCommandsInCurrentFrame;
     bool m_currentFrameHasExpensiveOp;
     bool m_previousFrameHasExpensiveOp;
     OwnPtr<RecordingImageBufferFallbackSurfaceFactory> m_fallbackFactory;
 };
 
 } // namespace blink
 
 #endif