Initial implementation of display list backed 2D canvases

Source/platform/graphics/GraphicsContext.cpp

Index: Source/platform/graphics/GraphicsContext.cpp
diff --git a/Source/platform/graphics/GraphicsContext.cpp b/Source/platform/graphics/GraphicsContext.cpp
index d9e0b831e230952e687e3fb150246833f868a342..e548c3294482fba486f77d95d65b081b18ad38ca 100644
--- a/Source/platform/graphics/GraphicsContext.cpp
+++ b/Source/platform/graphics/GraphicsContext.cpp
@@ -155,6 +155,13 @@ GraphicsContext::~GraphicsContext()
 #endif
 }
 
+void GraphicsContext::resetCanvas(SkCanvas* canvas)
+{
+    ASSERT(canvas);
+    m_canvas = canvas;
+    m_opaqueRegion.reset();

[dshwang, 2014/07/14 11:45:40]

Don't we need to reset m_paintState, m_paintStateIndex, m_pendingCanvasSave and
etc? If not, imho this api is difficult to use.
How about creating new GraphicsContext when creating new m_currentContext?

[Justin Novosad, 2014/07/17 18:34:14]

To be spec compliant, we have to retain the state. The
recordingImageBufferSurface is responsible for transferring the state from the
old SkCanvas to the new one so that it remains in sync with the GraphicsContext.

+}
+
 void GraphicsContext::save()
 {
     if (contextDisabled())
@@ -1044,6 +1051,22 @@ void GraphicsContext::drawImageBuffer(ImageBuffer* image, const FloatRect& dest,
     image->draw(this, dest, src, op);
 }
 
+void GraphicsContext::drawPicture(PassRefPtr<SkPicture> picture, const FloatRect& dest, const FloatRect& src, CompositeOperator op, WebBlendMode blendMode)
+{
+    if (contextDisabled() || !picture)
+        return;
+
+    SkPaint picturePaint;
+    picturePaint.setXfermode(WebCoreCompositeToSkiaComposite(op, blendMode).get());
+    SkRect skBounds = WebCoreFloatRectToSKRect(dest);
+    saveLayer(&skBounds, &picturePaint);
+    SkMatrix pictureTransform;
+    pictureTransform.setRectToRect(WebCoreFloatRectToSKRect(src), skBounds, SkMatrix::kFill_ScaleToFit);
+    m_canvas->concat(pictureTransform);
+    picture->draw(m_canvas);
+    restoreLayer();
+}
+
 void GraphicsContext::writePixels(const SkImageInfo& info, const void* pixels, size_t rowBytes, int x, int y)
 {
     if (contextDisabled())