Update BackingStore to handle the case where our Cocoa view has...

chrome/browser/renderer_host/backing_store.h

Index: chrome/browser/renderer_host/backing_store.h
===================================================================
--- chrome/browser/renderer_host/backing_store.h	(revision 24883)
+++ chrome/browser/renderer_host/backing_store.h	(working copy)
@@ -64,6 +64,10 @@
   // A CGLayer that stores the contents of the backing store, cached in GPU
   // memory if possible.
   CGLayerRef cg_layer() { return cg_layer_; }
+  // A CGBitmapContext that stores the contents of the backing store if the
+  // corresponding Cocoa view has not been inserted into an NSWindow yet.
+  CGContextRef cg_bitmap() { return cg_bitmap_; }
+
   // Paint the layer into a graphics context--if the target is a window,
   // this should be a GPU->GPU copy (and therefore very fast).
   void PaintToRect(const gfx::Rect& dest_rect, CGContextRef target);
@@ -118,6 +122,7 @@
   // Number of bits per pixel of the screen.
   int color_depth_;
 #elif defined(OS_MACOSX)
+  scoped_cftyperef<CGContextRef> cg_bitmap_;
   scoped_cftyperef<CGLayerRef> cg_layer_;
 #elif defined(OS_LINUX)
   // Paints the bitmap from the renderer onto the backing store without