Ensure that the WebstoreInstaller is always deleted on the UI thread

chrome/browser/extensions/webstore_installer.cc

 // 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.
 
 #include "chrome/browser/extensions/webstore_installer.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
@@ skipping 170 matching lines @@
       controller_(controller),
       id_(id),
       download_item_(NULL),
       flags_(flags),
       approval_(approval.release()) {
   // TODO(benjhayden): Change this CHECK to DCHECK after http://crbug.com/126013
   CHECK(controller_);
   download_url_ = GetWebstoreInstallURL(id, flags & FLAG_INLINE_INSTALL ?
       kInlineInstallSource : kDefaultInstallSource);
 
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   registrar_.Add(this, chrome::NOTIFICATION_CRX_INSTALLER_DONE,
                  content::NotificationService::AllSources());
   registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_INSTALLED,
                  content::Source<Profile>(profile->GetOriginalProfile()));
   registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_INSTALL_ERROR,
                  content::Source<CrxInstaller>(NULL));
 }
 
 void WebstoreInstaller::Start() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ skipping 152 matching lines @@
 void WebstoreInstaller::ReportSuccess() {
   if (delegate_) {
     delegate_->OnExtensionInstallSuccess(id_);
     delegate_ = NULL;
   }
 
   Release();  // Balanced in Start().
 }
 
 }  // namespace extensions