Disable delegation to picker controller once it is deleted.

chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm

 // Copyright (c) 2012 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 "chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.h"
 
 #include <Cocoa/Cocoa.h>
 
 #include "base/mac/foundation_util.h"
 #include "base/message_loop.h"
@@ skipping 26 matching lines @@
 }
 
 WebIntentPickerCocoa2::~WebIntentPickerCocoa2() {
 }
 
 void WebIntentPickerCocoa2::Close() {
   constrained_window_->CloseConstrainedWindow();
 }
 
 void WebIntentPickerCocoa2::SetActionString(const string16& action) {
-  // Ignored. Action string it retrieved from the model.
+  // Ignored. Action string is retrieved from the model.
 }
 
 void WebIntentPickerCocoa2::OnExtensionInstallSuccess(const std::string& id) {
   [view_controller_ update];
 }
 
 void WebIntentPickerCocoa2::OnExtensionInstallFailure(const std::string& id) {
   [view_controller_ update];
 }
 
@@ skipping 19 matching lines @@
   ChromeEventProcessingWindow* window =
       base::mac::ObjCCastStrict<ChromeEventProcessingWindow>(
           constrained_window_->GetNativeWindow());
   [window redispatchKeyEvent:event.os_event];
 }
 
 void WebIntentPickerCocoa2::OnPendingAsyncCompleted() {
   [view_controller_ update];
 }
 
+void WebIntentPickerCocoa2::InvalidateDelegate() {
+  delegate_ = NULL;
+}
+
 void WebIntentPickerCocoa2::OnInlineDispositionWebContentsLoaded(
     content::WebContents* web_contents) {
   [view_controller_ update];
 }
 
 gfx::Size WebIntentPickerCocoa2::GetMinInlineDispositionSize() {
   return [view_controller_ minimumInlineWebViewSize];
 }
 
 void WebIntentPickerCocoa2::OnModelChanged(WebIntentPickerModel* model) {
@@ skipping 15 matching lines @@
                                                 const GURL& url) {
   [view_controller_ update];
 }
 
 void WebIntentPickerCocoa2::OnConstrainedWindowClosed(
     ConstrainedWindowMac2* window) {
   // After the OnClosing call the model may be deleted so unset this reference.
   model_->set_observer(NULL);
   model_ = NULL;
 
-  delegate_->OnClosing();
+  if (delegate_)
+    delegate_->OnClosing();
   MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }