Don't crash when quitting while an extension popup is open.

chrome/browser/ui/cocoa/extensions/extension_popup_controller.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/extensions/extension_popup_controller.h"
 
 #include <algorithm>
 
 #include "chrome/browser/devtools/devtools_window.h"
 #include "chrome/browser/extensions/extension_host.h"
@@ skipping 183 matching lines @@
 
 - (void)showDevTools {
   DevToolsWindow::OpenDevToolsWindow(host_->render_view_host());
 }
 
 - (void)windowWillClose:(NSNotification *)notification {
   [super windowWillClose:notification];
   gPopup = nil;
   if (host_->view())
     host_->view()->set_container(NULL);
+  host_.reset();
 }
 
 - (void)windowDidResignKey:(NSNotification*)notification {
   if (!beingInspected_)
     [super windowDidResignKey:notification];
 }
 
 - (BOOL)isClosing {
   return [static_cast<InfoBubbleWindow*>([self window]) isClosing];
 }
@@ skipping 158 matching lines @@
   return minSize;
 }
 
 // Private (TestingAPI)
 + (NSSize)maxPopupSize {
   NSSize maxSize = {ExtensionViewMac::kMaxWidth, ExtensionViewMac::kMaxHeight};
   return maxSize;
 }
 
 @end