MacViews: Add native drop shadow to dialogs on OSX < 10.10.

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 9f6fbb505661a5a84985412dbe16f3958c7957e7..f4b6a867cd7c56da72d142f05aa21551bf6a6cc8 100644
--- a/ui/views/cocoa/bridged_content_view.h
+++ b/ui/views/cocoa/bridged_content_view.h
@@ -47,6 +47,9 @@ 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.
+  base::scoped_nsobject<NSBezierPath> windowMask_;
 }
 
 @property(readonly, nonatomic) views::View* hostedView;
@@ -73,6 +76,9 @@ 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.
+- (void)updateWindowMask;
+
 @end
 
 #endif  // UI_VIEWS_COCOA_BRIDGED_CONTENT_VIEW_H_