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

ui/views/cocoa/bridged_content_view.h

 // Copyright 2014 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 UI_VIEWS_COCOA_BRIDGED_CONTENT_VIEW_H_
 #define UI_VIEWS_COCOA_BRIDGED_CONTENT_VIEW_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/strings/string16.h"
@@ skipping 22 matching lines @@
   ui::TextInputClient* textInputClient_;
 
   // A tracking area installed to enable mouseMoved events.
   ui::ScopedCrTrackingArea cursorTrackingArea_;
 
   // Whether the view is reacting to a keyDown event on the view.
   BOOL inKeyDown_;
 
   // 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;
 
 // Clear the hosted view. For example, if it is about to be destroyed.
 - (void)clearView;
 
 // Process a mouse event captured while the widget had global mouse capture.
 - (void)processCapturedMouseEvent:(NSEvent*)theEvent;
 
 // Mac's version of views::corewm::TooltipController::UpdateIfRequired().
 // Updates the tooltip on the ToolTipBaseView if the text needs to change.
 // |locationInContent| is the position from the top left of the window's
 // contentRect (also this NSView's frame), as given by a ui::LocatedEvent.
 - (void)updateTooltipIfRequiredAt:(const gfx::Point&)locationInContent;
 
 @end
 
 #endif  // UI_VIEWS_COCOA_BRIDGED_CONTENT_VIEW_H_