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

chrome/browser/background/background_contents.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_
 #define CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "extensions/browser/delayed_start_render_host.h"
 #include "ui/base/window_open_disposition.h"
+#include "url/gurl.h"
 
 class Profile;
 
 namespace content {
 class SessionStorageNamespace;
 class SiteInstance;
 };
 
 // This class maintains a WebContents used in the background. It can host a
 // renderer, but does not have any visible display.
 // TODO(atwilson): Unify this with background pages; http://crbug.com/77790
-class BackgroundContents : public content::WebContentsDelegate,
+class BackgroundContents : public extensions::DelayedStartRenderHost,
+                           public content::WebContentsDelegate,
                            public content::WebContentsObserver,
                            public content::NotificationObserver {
  public:
   class Delegate {
    public:
     // Called by AddNewContents(). Asks the delegate to attach the opened
     // WebContents to a suitable container (e.g. browser) or to show it if it's
     // a popup window. If |was_blocked| is non-NULL, then |*was_blocked| will be
     // set to true if the popup gets blocked, and left unchanged otherwise.
     virtual void AddWebContents(content::WebContents* new_contents,
@@ skipping 11 matching lines @@
       int routing_id,
       int main_frame_routing_id,
       Delegate* delegate,
       const std::string& partition_id,
       content::SessionStorageNamespace* session_storage_namespace);
   ~BackgroundContents() override;
 
   content::WebContents* web_contents() const { return web_contents_.get(); }
   virtual const GURL& GetURL() const;
 
+  // Adds this BackgroundContents to the queue of RenderViews to create.
+  void CreateRenderViewSoon(const GURL& url);
+
+  // DelayedStartRenderHost implementation:
+  void CreateRenderViewNow() override;

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

We can actually make this private now (same for extension_host.h) and move the
"DO NOT USE" comment just to DelayedStartRenderHost.

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

Cool, I didn't know you could do that.

[Devlin, 2015/02/19 16:41:43]

Handy for these implementation-detail-type interfaces. :)

+
   // content::WebContentsDelegate implementation:
   void CloseContents(content::WebContents* source) override;
   bool ShouldSuppressDialogs(content::WebContents* source) override;
   void DidNavigateMainFramePostCommit(content::WebContents* tab) override;
   void AddNewContents(content::WebContents* source,
                       content::WebContents* new_contents,
                       WindowOpenDisposition disposition,
                       const gfx::Rect& initial_rect,
                       bool user_gesture,
                       bool* was_blocked) override;
@@ skipping 12 matching lines @@
   BackgroundContents();
 
  private:
   // The delegate for this BackgroundContents.
   Delegate* delegate_;
 
   Profile* profile_;
   scoped_ptr<content::WebContents> web_contents_;
   content::NotificationRegistrar registrar_;
 
+  // The initial URL to load.
+  GURL initial_url_;
+
   DISALLOW_COPY_AND_ASSIGN(BackgroundContents);
 };
 
 // This is the data sent out as the details with BACKGROUND_CONTENTS_OPENED.
 struct BackgroundContentsOpenedDetails {
   // The BackgroundContents object that has just been opened.
   BackgroundContents* contents;
 
   // The name of the parent frame for these contents.
   const base::string16& frame_name;
 
   // The ID of the parent application (if any).
   const base::string16& application_id;
 };
 
 #endif  // CHROME_BROWSER_BACKGROUND_BACKGROUND_CONTENTS_H_