Adds a bounds parameter to ui::Compositor::ReadPixels

ui/gfx/compositor/compositor.h

Index: ui/gfx/compositor/compositor.h
diff --git a/ui/gfx/compositor/compositor.h b/ui/gfx/compositor/compositor.h
index 23fff5b728948039f1a8ec011190cef0061fc702..2b41553d391e6bf43de20aceacfef77249e9f45b 100644
--- a/ui/gfx/compositor/compositor.h
+++ b/ui/gfx/compositor/compositor.h
@@ -136,9 +136,10 @@ class COMPOSITOR_EXPORT Compositor : public base::RefCounted<Compositor> {
   // compositing.
   void Draw(bool force_clear);
 
-  // Reads the contents of the last rendered frame into the given bitmap.
+  // Reads the region |bounds| of the contents of the last rendered frame
+  // into the given bitmap.
   // Returns false if the pixels could not be read.
-  virtual bool ReadPixels(SkBitmap* bitmap) = 0;
+  virtual bool ReadPixels(SkBitmap* bitmap, const gfx::Rect& bounds) = 0;
 
   // Notifies the compositor that the size of the widget that it is
   // drawing to has changed.