Fix flipped views on Mac

content/browser/renderer_host/render_widget_host_view_mac.h

Index: content/browser/renderer_host/render_widget_host_view_mac.h
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 3abfb1d479f6bd85862d9f4fce79eceb648869e9..6d3987ab01cc76932eb59006c8d408f7efcaa92a 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -411,9 +411,16 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   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_;