Transfer canvas state to the next frame with noticable restrictions.

Source/platform/graphics/RecordingImageBufferSurface.h

Index: Source/platform/graphics/RecordingImageBufferSurface.h
diff --git a/Source/platform/graphics/RecordingImageBufferSurface.h b/Source/platform/graphics/RecordingImageBufferSurface.h
index c8af6a045081ddfc38190d3bd03f27eb84842e20..a3d887e274115296f3a039ede26522ac64f0db7e 100644
--- a/Source/platform/graphics/RecordingImageBufferSurface.h
+++ b/Source/platform/graphics/RecordingImageBufferSurface.h
@@ -7,6 +7,8 @@
 
 #include "platform/graphics/ImageBufferSurface.h"
 #include "public/platform/WebThread.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "wtf/Deque.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/RefPtr.h"
 
@@ -18,6 +20,17 @@ namespace blink {
 
 class ImageBuffer;
 

[Sergey, 2014/08/28 09:55:34]

I am not sure, that this declarations belong here... Please, let me know if I
should refactor it somehow.

+// The same with the default state stack size in SkCanvas
+#define INITIAL_STATE_STACK_SIZE 1
+
+struct StateRec {

[Justin Novosad, 2014/08/28 14:53:00]

This struct and the typedef below should be moved to the 'private' section of
RecordingImageBufferSurface.

[Sergey, 2014/09/03 01:50:51]

Done.

+public:
+    SkMatrix m_ctm;
+    SkRect m_clip;
+};
+
+typedef Deque<StateRec, INITIAL_STATE_STACK_SIZE> StateStack;
+
 class PLATFORM_EXPORT RecordingImageBufferSurface : public ImageBufferSurface {
     WTF_MAKE_NONCOPYABLE(RecordingImageBufferSurface); WTF_MAKE_FAST_ALLOCATED;
 public:
@@ -39,6 +52,11 @@ private:
     void initializeCurrentFrame();
     bool finalizeFrameInternal();
 
+    // saves current clip and transform matrix of canvas
+    bool saveState(SkCanvas*, StateStack*);
+    // we should make sure that we can transfer state in saveState
+    void setCurrentState(SkCanvas*, StateStack*);
+
     OwnPtr<SkPictureRecorder> m_currentFrame;
     RefPtr<SkPicture> m_previousFrame;
     OwnPtr<SkCanvas> m_rasterCanvas;