[MacViews] Enable dragging a window by its caption/draggable areas.

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 969af9975a1997862949dffe3a31086e7527e380..49b41dca21cc7ed1d2809c6fd304a3da47d6f645 100644
--- a/ui/views/cocoa/bridged_content_view.h
+++ b/ui/views/cocoa/bridged_content_view.h
@@ -40,11 +40,19 @@ class View;
 
   // The last tooltip text, used to limit updates.
   base::string16 lastTooltipText_;
+
+  // Whether dragging on the view moves the window.
+  BOOL mouseDownCanMoveWindow_;
 }
 
 @property(readonly, nonatomic) views::View* hostedView;
 @property(assign, nonatomic) ui::TextInputClient* textInputClient;
 
+// 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
+// so that BridgedNativeWidget can dynamically enable dragging of the window.
+@property(assign) BOOL mouseDownCanMoveWindow;
+
 // Initialize the NSView -> views::View bridge. |viewToHost| must be non-NULL.
 - (id)initWithView:(views::View*)viewToHost;