Fix race conditions in window snapshot code.

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index f3f5c7fe6f96b89c9103a75a30a8772052572acf..97d5f2f75e8854012475c2c40e692e532c675b52 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -213,6 +213,8 @@ class CONTENT_EXPORT RenderWidget
 
   bool is_swapped_out() { return is_swapped_out_; }
 
+  void ScheduleCompositeWithForcedRedraw();
+
  protected:
   // Friend RefCounted so that the dtor can be non-public. Using this class
   // without ref-counting is an error.
@@ -517,6 +519,8 @@ class CONTENT_EXPORT RenderWidget
 
   bool OnSnapshotHelper(const gfx::Rect& src_subrect, SkBitmap* bitmap);
 
+  void ScheduleCompositeImpl(bool force_redraw);
+
   // Routing ID that allows us to communicate to the parent browser process
   // RenderWidgetHost. When MSG_ROUTING_NONE, no messages may be sent.
   int32 routing_id_;