Make BackgroundContentsService start up BackgroundContents with a delay, as for ExtensionHosts.

chrome/browser/background/background_contents_service.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/background/background_contents_service.h"
 
 #include "apps/app_load_service.h"
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 616 matching lines @@
   BackgroundContents* contents = CreateBackgroundContents(
       SiteInstance::CreateForURL(profile, url),
       MSG_ROUTING_NONE,
       MSG_ROUTING_NONE,
       profile,
       frame_name,
       application_id,
       std::string(),
       NULL);
 
-  // TODO(atwilson): Create RenderViews asynchronously to avoid increasing
-  // startup latency (http://crbug.com/47236).
-  contents->web_contents()->GetController().LoadURL(
-      url, content::Referrer(), ui::PAGE_TRANSITION_LINK, std::string());
+  contents->CreateRenderViewSoon(url);
 }
 
 BackgroundContents* BackgroundContentsService::CreateBackgroundContents(
     SiteInstance* site,
     int routing_id,
     int main_frame_route_id,
     Profile* profile,
     const base::string16& frame_name,
     const base::string16& application_id,
     const std::string& partition_id,
     content::SessionStorageNamespace* session_storage_namespace) {
   BackgroundContents* contents = new BackgroundContents(
       site, routing_id, main_frame_route_id, this, partition_id,
       session_storage_namespace);
 
   // Register the BackgroundContents internally, then send out a notification
   // to external listeners.
   BackgroundContentsOpenedDetails details = {contents,
                                              frame_name,
                                              application_id};
   BackgroundContentsOpened(&details, profile);

[Devlin, 2015/02/18 23:22:12]

Andrew will probably know better, but do we need to adjust these
(BackgroundContentsOpened(), sending the notifications) at all?  (They still
happened before the render was created, but there was a bit less of a gap -
particularly if we experiment with more than just a "post-task-at-end-of-queue
ExtensionHostQueue implementation.)

[Yoyo Zhou, 2015/02/19 02:55:37]

Adding tengs to comment, since DriveWebContentsManager is the only observer of
this notification.

   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_BACKGROUND_CONTENTS_OPENED,
       content::Source<Profile>(profile),
       content::Details<BackgroundContentsOpenedDetails>(&details));
 
   // A new background contents has been created - notify our listeners.
   SendChangeNotification(profile);
   return contents;
 }
 
@@ skipping 103 matching lines @@
     bool user_gesture,
     bool* was_blocked) {
   Browser* browser = chrome::FindLastActiveWithProfile(
       Profile::FromBrowserContext(new_contents->GetBrowserContext()),
       chrome::GetActiveDesktop());
   if (browser) {
     chrome::AddWebContents(browser, NULL, new_contents, disposition,
                            initial_rect, user_gesture, was_blocked);
   }
 }