Move code in src/remoting to the new callbacks.

remoting/host/continue_window_mac.mm

 // Copyright (c) 2011 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.
 
 #include "remoting/host/continue_window.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ skipping 125 matching lines @@
   // Remove window shade.
   for (NSWindow* window in shades_.get()) {
     [window close];
   }
   shades_.reset();
   continue_alert_.reset();
 }
 
 - (void)onCancel:(id)sender {
   [self hide];
-  host_->Shutdown(NULL);
+  host_->Shutdown(base::Closure());
   host_ = nil;
 }
 
 - (void)onContinue:(id)sender {
   [self hide];
   host_->PauseSession(false);
   host_ = nil;
 }
 
 @end