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

chrome/browser/background/background_contents.h

Index: chrome/browser/background/background_contents.h
diff --git a/chrome/browser/background/background_contents.h b/chrome/browser/background/background_contents.h
index e7345e344c7c6572da0f1e721f105d6c3e941742..8b2815b1e70463cad3874f72eae8da8863f483a8 100644
--- a/chrome/browser/background/background_contents.h
+++ b/chrome/browser/background/background_contents.h
@@ -12,7 +12,9 @@
 #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;
 
@@ -24,7 +26,8 @@ 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:
@@ -56,6 +59,12 @@ class BackgroundContents : public content::WebContentsDelegate,
   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;
@@ -88,6 +97,9 @@ class BackgroundContents : public content::WebContentsDelegate,
   scoped_ptr<content::WebContents> web_contents_;
   content::NotificationRegistrar registrar_;
 
+  // The initial URL to load.
+  GURL initial_url_;
+
   DISALLOW_COPY_AND_ASSIGN(BackgroundContents);
 };