MacViews: Fix failing mouse capture unittests.

ui/views/cocoa/bridged_native_widget.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_NATIVE_WIDGET_H_
 #define UI_VIEWS_COCOA_BRIDGED_NATIVE_WIDGET_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ skipping 223 matching lines @@
   // Show the window using -[NSApp beginSheet:..], modal for the parent window.
   void ShowAsModalSheet();
 
   // Sets mouseDownCanMoveWindow on |bridged_view_| and triggers the NSWindow to
   // update its draggable region.
   void SetDraggable(bool draggable);
 
   // Overridden from CocoaMouseCaptureDelegate:
   void PostCapturedEvent(NSEvent* event) override;
   void OnMouseCaptureLost() override;
+  NSWindow* GetWindow() const override;
 
   // Returns a properties dictionary associated with the NSWindow.
   // Creates and attaches a new instance if not found.
   NSMutableDictionary* GetWindowProperties() const;
 
   // Overridden from FocusChangeListener:
   void OnWillChangeFocus(View* focused_before,
                          View* focused_now) override;
   void OnDidChangeFocus(View* focused_before,
                         View* focused_now) override;
@@ skipping 61 matching lines @@
   bool invalidate_shadow_on_frame_swap_ = false;
 
   AssociatedViews associated_views_;
 
   DISALLOW_COPY_AND_ASSIGN(BridgedNativeWidget);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_COCOA_BRIDGED_NATIVE_WIDGET_H_