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

extensions/browser/extension_host_delegate.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_DELEGATE_H_
 #define EXTENSIONS_BROWSER_EXTENSION_HOST_DELEGATE_H_
 
 #include <string>
 
 #include "content/public/common/media_stream_request.h"
 #include "ui/base/window_open_disposition.h"
 
 namespace content {
 class JavaScriptDialogManager;
 class WebContents;
 }
 
 namespace gfx {
 class Rect;
 }
 
 namespace extensions {
 class Extension;
 class ExtensionHost;
+class ExtensionHostQueue;
 
 // A delegate to support functionality that cannot exist in the extensions
 // module. This is not an inner class of ExtensionHost to allow it to be forward
 // declared.
 class ExtensionHostDelegate {
  public:
   virtual ~ExtensionHostDelegate() {}
 
   // Called after the hosting |web_contents| for an extension is created. The
   // implementation may wish to add preference observers to |web_contents|.
@@ skipping 22 matching lines @@
       const content::MediaResponseCallback& callback,
       const Extension* extension) = 0;
 
   // Checks if we have permission to access the microphone or camera. Note that
   // this does not query the user. |type| must be MEDIA_DEVICE_AUDIO_CAPTURE
   // or MEDIA_DEVICE_VIDEO_CAPTURE.
   virtual bool CheckMediaAccessPermission(content::WebContents* web_contents,
                                           const GURL& security_origin,
                                           content::MediaStreamType type,
                                           const Extension* extension) = 0;
+
+  // Returns the ExtensionHostQueue implementation to use for creating
+  // ExtensionHost renderers.
+  virtual ExtensionHostQueue* GetExtensionHostQueue() const = 0;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_HOST_DELEGATE_H_