For Mac, add AppListViewDelegateObserver::OnShutdown

ui/app_list/cocoa/app_list_view_controller.mm

 // Copyright 2013 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/app_list/cocoa/app_list_view_controller.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 70 matching lines @@
 namespace app_list {
 
 class AppListModelObserverBridge : public AppListViewDelegateObserver {
  public:
   AppListModelObserverBridge(AppListViewController* parent);
   virtual ~AppListModelObserverBridge();
 
  private:
   // Overridden from app_list::AppListViewDelegateObserver:
   virtual void OnProfilesChanged() OVERRIDE;
+  virtual void OnShutdown() OVERRIDE;
 
   AppListViewController* parent_;  // Weak. Owns us.
 
   DISALLOW_COPY_AND_ASSIGN(AppListModelObserverBridge);
 };
 
 AppListModelObserverBridge::AppListModelObserverBridge(
     AppListViewController* parent)
     : parent_(parent) {
   [parent_ delegate]->AddObserver(this);
 }
 
 AppListModelObserverBridge::~AppListModelObserverBridge() {
   [parent_ delegate]->RemoveObserver(this);
 }
 
 void AppListModelObserverBridge::OnProfilesChanged() {
   [parent_ onProfilesChanged];
 }
 
+void AppListModelObserverBridge::OnShutdown() {
+  [parent_ setDelegate:nil];
+}
+
 }  // namespace app_list
 
 @implementation AppListViewController
 
 - (id)init {
   if ((self = [super init])) {
     appsGridController_.reset([[AppsGridController alloc] init]);
     [self loadAndSetView];
 
     [self totalPagesChanged];
@@ skipping 237 matching lines @@
 
 - (void)redoSearch {
   [self modelTextDidChange];
 }
 
 - (void)onProfilesChanged {
   [appsSearchBoxController_ rebuildMenu];
 }
 
 @end