2D canvas: fix shadow rendering with compositing modes that require temp layers

Source/platform/graphics/GraphicsTypes.h

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 54 matching lines @@
     CompositeDestinationOver,
     CompositeDestinationIn,
     CompositeDestinationOut,
     CompositeDestinationAtop,
     CompositeXOR,
     CompositePlusDarker,
     CompositePlusLighter,
     CompositeDifference
 };
 
+enum ShadowMode {
+    DrawShadowAndForeground,
+    DrawShadowOnly,
+    DrawForegroundOnly

[jbroman, 2014/10/14 21:09:48]

This doesn't sound like a shadow mode to me; why not just clear the shadow in
this case?

+};
+
 enum GradientSpreadMethod {
     SpreadMethodPad,
     SpreadMethodReflect,
     SpreadMethodRepeat
 };
 
 enum LineCap {
     ButtCap = SkPaint::kButt_Cap,
     RoundCap = SkPaint::kRound_Cap,
     SquareCap = SkPaint::kSquare_Cap
@@ skipping 40 matching lines @@
 
 PLATFORM_EXPORT String textAlignName(TextAlign);
 PLATFORM_EXPORT bool parseTextAlign(const String&, TextAlign&);
 
 PLATFORM_EXPORT String textBaselineName(TextBaseline);
 PLATFORM_EXPORT bool parseTextBaseline(const String&, TextBaseline&);
 
 } // namespace blink
 
 #endif