Switching to SkDeferredCanvas factory API in preparation for constructor deprecation

Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp

Index: Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
diff --git a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
index 3e9a705859bed05d9177823dc8e2cc40cb2aba9d..b1822ad6475fa139fe828ea848b1b6d322d9ed8a 100644
--- a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
+++ b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
@@ -65,7 +65,7 @@ PassOwnPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(PassRefPtr<GraphicsC
     SkAutoTUnref<SkSurface> surface(createSurface(context.get(), size));
     if (!surface.get())
         return PassOwnPtr<Canvas2DLayerBridge>();
-    SkDeferredCanvas* canvas = new SkDeferredCanvas(surface);
+    SkDeferredCanvas* canvas = SkDeferredCanvas::Create(surface.get());
     OwnPtr<Canvas2DLayerBridge> layerBridge = adoptPtr(new Canvas2DLayerBridge(context, canvas, opacityMode));

[Stephen White, 2013/08/08 18:04:59]

Not new to this patch, but the ownership semantics of the deferred canvas are
really unclear here.

The canvas is allocated here, and passed to the Canavs2DLayerBridge constructor.
The bridge never refs it, but also never unrefs it, and neither does this
factory function. It seems like it's just temporarily unowned, until the
ImageBuffer refs it over in ImageBuffer, while Canvas2DLayerBridge keeps a bare
pointer to it. That seems really fragile. If you just create a bridge, and never
ref the canvas in it, it'll leak. If the bridge ever outlives the ImageBuffer,
it'll blow up (I realize that doesn't happen now, but the dependency is not
explicit).

Is there any way we could clean this up?

     return layerBridge.release();
 }