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

ui/views/cocoa/views_nswindow_delegate.mm

 // 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.
 
 #import "ui/views/cocoa/views_nswindow_delegate.h"
 
 #include "base/logging.h"
 #import "ui/views/cocoa/bridged_content_view.h"
 #import "ui/views/cocoa/bridged_native_widget.h"
 #include "ui/views/widget/native_widget_mac.h"
@@ skipping 36 matching lines @@
   parent_->OnVisibilityChangedTo(true);
 }
 
 - (void)sheetDidEnd:(NSWindow*)sheet
          returnCode:(NSInteger)returnCode
         contextInfo:(void*)contextInfo {
   [sheet orderOut:nil];
   parent_->OnWindowWillClose();
 }
 
+- (BOOL)onWindowWillReceiveLeftMouseDown:(NSPoint)locationInWindow {
+  return parent_->OnWindowWillReceiveLeftMouseDown(locationInWindow);
+}
+
 // NSWindowDelegate implementation.
 
 - (void)windowDidFailToEnterFullScreen:(NSWindow*)window {
   // Cocoa should already have sent an (unexpected) windowDidExitFullScreen:
   // notification, and the attempt to get back into fullscreen should fail.
   // Nothing to do except verify |parent_| is no longer trying to fullscreen.
   DCHECK(!parent_->target_fullscreen_state());
 }
 
 - (void)windowDidFailToExitFullScreen:(NSWindow*)window {
@@ skipping 43 matching lines @@
 
 - (void)windowWillExitFullScreen:(NSNotification*)notification {
   parent_->OnFullscreenTransitionStart(false);
 }
 
 - (void)windowDidExitFullScreen:(NSNotification*)notification {
   parent_->OnFullscreenTransitionComplete(false);
 }
 
 @end