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

ui/views/cocoa/views_nswindow_delegate.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_VIEWS_NSWINDOW_DELEGATE_H_
 #define UI_VIEWS_COCOA_VIEWS_NSWINDOW_DELEGATE_H_
 
 #import <Cocoa/Cocoa.h>
 
 #import "base/mac/scoped_nsobject.h"
@@ skipping 34 matching lines @@
 - (void)onWindowOrderChanged:(NSNotification*)notification;
 
 // Notify when -[NSWindow display] is being called on the window.
 - (void)onWindowWillDisplay;
 
 // Called on the delegate of a modal sheet when its modal session ends.
 - (void)sheetDidEnd:(NSWindow*)sheet
          returnCode:(NSInteger)returnCode
         contextInfo:(void*)contextInfo;
 
+// Called when the application receives a mouse-down, but before the event
+// is processed by NSWindows. Returns NO if the event should be processed as-is,
+// or YES if the event should be reposted to handle window dragging. Events are
+// reposted at the CGSessionEventTap level because window dragging happens there
+// before the application receives the event.
+- (BOOL)shouldRepostPendingLeftMouseDown:(NSPoint)locationInWindow;
+
 @end
 
 #endif  // UI_VIEWS_COCOA_VIEWS_NSWINDOW_DELEGATE_H_