Fix flipped views on Mac

content/browser/renderer_host/render_widget_host_view_mac.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <IOSurface/IOSurfaceAPI.h>
 #include <list>
@@ skipping 393 matching lines @@
 
   // The associated Model.  Can be NULL if Destroy() is called when
   // someone (other than superview) has retained |cocoa_view_|.
   RenderWidgetHostImpl* render_widget_host_;
 
   // Current text input type.
   ui::TextInputType text_input_type_;
   bool can_compose_inline_;
 
   // The background CoreAnimation layer which is hosted by |cocoa_view_|.
-  // The compositing or software layers will be added as sublayers to this.
   base::scoped_nsobject<CALayer> background_layer_;
 
+  // A flipped layer, which acts as the parent of the compositing and software
+  // layers. This layer is flipped so that the we don't need to recompute the
+  // origin for sub-layers when their position changes (this is impossible when
+  // using remote layers, as their size change cannot be synchronized with the
+  // window). This indirection is needed because flipping hosted layers (like
+  // |background_layer_|) leads to unpredictable behavior.
+  base::scoped_nsobject<CALayer> flipped_layer_;
+
   // The CoreAnimation layer hosted by the GPU process.
   base::scoped_nsobject<CALayerHost> remote_layer_host_;
 
   // The CoreAnimation layer for software compositing. This should be NULL
   // when software compositing is not in use.
   base::scoped_nsobject<SoftwareLayer> software_layer_;
 
   // Accelerated compositing structures. These may be dynamically created and
   // destroyed together in Create/DestroyCompositedIOSurfaceAndLayer.
   base::scoped_nsobject<CompositingIOSurfaceLayer> compositing_iosurface_layer_;
@@ skipping 183 matching lines @@
   scoped_ptr<RenderWidgetHostViewFrameSubscriber> frame_subscriber_;
 
   base::WeakPtrFactory<RenderWidgetHostViewMac>
       software_frame_weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_