MacViews: Clip contents for non-rectangular windows.

ui/views/cocoa/bridged_content_view.h

Index: ui/views/cocoa/bridged_content_view.h
diff --git a/ui/views/cocoa/bridged_content_view.h b/ui/views/cocoa/bridged_content_view.h
index f4b6a867cd7c56da72d142f05aa21551bf6a6cc8..1ceb1a10fc9c5ead498e8c06f565caa4e194c44b 100644
--- a/ui/views/cocoa/bridged_content_view.h
+++ b/ui/views/cocoa/bridged_content_view.h
@@ -48,13 +48,16 @@ class View;
   // Whether dragging on the view moves the window.
   BOOL mouseDownCanMoveWindow_;
 
-  // The cached window mask. Only used for non-rectangular windows on 10.9.
+  // The cached window mask. Only used for non-rectangular windows. Used to clip
+  // window boundary and generate drop shadow on OSX 10.9 and for clipping view
+  // contents in BridgedNativeWidget.
   base::scoped_nsobject<NSBezierPath> windowMask_;
 }
 
 @property(readonly, nonatomic) views::View* hostedView;
 @property(assign, nonatomic) ui::TextInputClient* textInputClient;
 @property(assign, nonatomic) BOOL drawMenuBackgroundForBlur;
+@property(readonly, nonatomic) NSBezierPath* windowMask;
 
 // Extends an atomic, readonly property on NSView to make it assignable.
 // This usually returns YES if the view is transparent. We want to control it
@@ -76,7 +79,7 @@ class View;
 // contentRect (also this NSView's frame), as given by a ui::LocatedEvent.
 - (void)updateTooltipIfRequiredAt:(const gfx::Point&)locationInContent;
 
-// Update windowMask_ depending on the current view bounds.
+// Update |windowMask_| depending on the current view bounds.
 - (void)updateWindowMask;
 
 @end