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

extensions/browser/extension_host.h

 // Copyright 2014 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 EXTENSIONS_BROWSER_EXTENSION_HOST_H_
 #define EXTENSIONS_BROWSER_EXTENSION_HOST_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/timer/elapsed_timer.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 "extensions/browser/extension_function_dispatcher.h"
 #include "extensions/common/stack_frame.h"
 #include "extensions/common/view_type.h"
 
 class PrefsTabHelper;
 
 namespace content {
 class BrowserContext;
 class RenderProcessHost;
 class RenderWidgetHostView;
 class SiteInstance;
 }
 
 namespace extensions {
 class Extension;
 class ExtensionHostDelegate;
 class ExtensionHostObserver;
 class ExtensionHostQueue;
 class WindowController;
 
 // This class is the browser component of an extension component's RenderView.
 // It handles setting up the renderer process, if needed, with special
 // privileges available to extensions.  It may have a view to be shown in the
 // browser UI, or it may be hidden.
 //
 // If you are adding code that only affects visible extension views (and not
 // invisible background pages) you should add it to ExtensionViewHost.
-class ExtensionHost : public content::WebContentsDelegate,
+class ExtensionHost : public DelayedStartRenderHost,
+                      public content::WebContentsDelegate,
                       public content::WebContentsObserver,
                       public ExtensionFunctionDispatcher::Delegate,
                       public content::NotificationObserver {
  public:
   ExtensionHost(const Extension* extension,
                 content::SiteInstance* site_instance,
                 const GURL& url, ViewType host_type);
   ~ExtensionHost() override;
 
   const Extension* extension() const { return extension_; }
@@ skipping 13 matching lines @@
 
   // Returns true if the render view is initialized and didn't crash.
   bool IsRenderViewLive() const;
 
   // Prepares to initializes our RenderViewHost by creating its RenderView and
   // navigating to this host's url. Uses host_view for the RenderViewHost's view
   // (can be NULL). This happens delayed to avoid locking the UI.
   void CreateRenderViewSoon();
 
   // DO NOT CALL THIS. Always use CreateRenderViewSoon().
-  // (Unless you're implementing an ExtensionHostQueue).
-  void CreateRenderViewNow();
+  // (Unless you're implementing an ExtensionHostQueue.)
+  // DelayedStartRenderHost:
+  void CreateRenderViewNow() override;
 
   // Closes this host (results in [possibly asynchronous] deletion).
   void Close();
 
   // Typical observer interface.
   void AddObserver(ExtensionHostObserver* observer);
   void RemoveObserver(ExtensionHostObserver* observer);
 
   // Called when an IPC message is dispatched to the RenderView associated with
   // this ExtensionHost.
   void OnMessageDispatched(const std::string& event_name, int message_id);
 
   // Called by the ProcessManager when a network request is started by the
   // extension corresponding to this ExtensionHost.
   void OnNetworkRequestStarted(uint64 request_id);
 
   // Called by the ProcessManager when a previously started network request is
   // finished.
   void OnNetworkRequestDone(uint64 request_id);
 
-  // content::WebContentsObserver
+  // content::WebContentsObserver:
   bool OnMessageReceived(const IPC::Message& message) override;
   void RenderViewCreated(content::RenderViewHost* render_view_host) override;
   void RenderViewDeleted(content::RenderViewHost* render_view_host) override;
   void RenderViewReady() override;
   void RenderProcessGone(base::TerminationStatus status) override;
   void DocumentAvailableInMainFrame() override;
   void DidStopLoading(content::RenderViewHost* render_view_host) override;
 
-  // content::WebContentsDelegate
+  // content::WebContentsDelegate:
   content::JavaScriptDialogManager* GetJavaScriptDialogManager(
       content::WebContents* source) override;
   void AddNewContents(content::WebContents* source,
                       content::WebContents* new_contents,
                       WindowOpenDisposition disposition,
                       const gfx::Rect& initial_rect,
                       bool user_gesture,
                       bool* was_blocked) override;
   void CloseContents(content::WebContents* contents) override;
   void RequestMediaAccessPermission(
       content::WebContents* web_contents,
       const content::MediaStreamRequest& request,
       const content::MediaResponseCallback& callback) override;
   bool CheckMediaAccessPermission(content::WebContents* web_contents,
                                   const GURL& security_origin,
                                   content::MediaStreamType type) override;
   bool IsNeverVisible(content::WebContents* web_contents) override;
 
-  // content::NotificationObserver
+  // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
  protected:
   content::NotificationRegistrar* registrar() { return &registrar_; }
 
   // Called after the extension page finishes loading but before the
   // EXTENSION_HOST_DID_STOP_LOADING notification is sent.
   virtual void OnDidStopLoading();
@@ skipping 54 matching lines @@
   scoped_ptr<base::ElapsedTimer> load_start_;
 
   ObserverList<ExtensionHostObserver> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionHost);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_HOST_H_