Create renderers for ExtensionHosts one a time to avoid blocking the UI.

chrome/browser/extensions/extension_process_manager.cc

 // Copyright (c) 2009 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/extension_process_manager.h"
 
 #include "chrome/browser/browsing_instance.h"
 #include "chrome/browser/extensions/extension_host.h"
 #include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/profile.h"
@@ skipping 68 matching lines @@
       return CreateView(extension, url, browser);
   }
   return NULL;
 }
 
 ExtensionHost* ExtensionProcessManager::CreateBackgroundHost(
     Extension* extension, const GURL& url) {
   ExtensionHost* host =
       new ExtensionHost(extension, GetSiteInstanceForURL(url), url,
                         ViewType::EXTENSION_BACKGROUND_PAGE);
-  host->CreateRenderView(NULL);  // create a RenderViewHost with no view
+  host->CreateRenderViewSoon(NULL);  // create a RenderViewHost with no view
   OnExtensionHostCreated(host, true);
   return host;
 }
 
 void ExtensionProcessManager::RegisterExtensionProcess(
     const std::string& extension_id, int process_id) {
   ProcessIDMap::const_iterator it = process_ids_.find(extension_id);
   if (it != process_ids_.end() && (*it).second == process_id)
     return;
 
@@ skipping 97 matching lines @@
 void ExtensionProcessManager::OnExtensionHostCreated(ExtensionHost* host,
                                                      bool is_background) {
   all_hosts_.insert(host);
   if (is_background)
     background_hosts_.insert(host);
   NotificationService::current()->Notify(
       NotificationType::EXTENSION_HOST_CREATED,
       Source<ExtensionProcessManager>(this),
       Details<ExtensionHost>(host));
 }