Implement interest rects for synchronized paint.

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

Index: third_party/WebKit/Source/platform/graphics/ContentLayerDelegate.h
diff --git a/third_party/WebKit/Source/platform/graphics/ContentLayerDelegate.h b/third_party/WebKit/Source/platform/graphics/ContentLayerDelegate.h
index 968e1073a4b2a35498a253982561b5a7da1314f3..6cf7c5d614d31b3febf45a2b2cdfc75498cf3653 100644
--- a/third_party/WebKit/Source/platform/graphics/ContentLayerDelegate.h
+++ b/third_party/WebKit/Source/platform/graphics/ContentLayerDelegate.h
@@ -42,6 +42,7 @@ class IntRect;
 class PLATFORM_EXPORT GraphicsContextPainter {
 public:
     virtual void paint(GraphicsContext&, const IntRect& clip) = 0;
+    virtual void paintIfNeeded(GraphicsContext&) = 0;

[wkorman, 2015/10/09 19:46:32]

Comment w/ some brief docs? Esp. re: this vs the other paint() methods. I sort
of feel this way about everything in the code base that says "xxxIfNeeded".

[chrishtr, 2015/10/09 20:54:52]

Done.

     virtual DisplayItemList* displayItemList() = 0;
 
 protected: