Prerendered pages are swapped in at browser::Navigate time.

content/browser/tab_contents/tab_contents.h

Index: content/browser/tab_contents/tab_contents.h
diff --git a/content/browser/tab_contents/tab_contents.h b/content/browser/tab_contents/tab_contents.h
index 56cd1cffa224df144e0d42efe0924fe97d12debf..d7cff6b8601ca88aba2eeaaa7bd0233c48de4029 100644
--- a/content/browser/tab_contents/tab_contents.h
+++ b/content/browser/tab_contents/tab_contents.h
@@ -113,6 +113,10 @@ class CONTENT_EXPORT TabContents
     opener_web_ui_type_ = opener_web_ui_type;
   }
 
+  void set_opener_origin(const GURL& opener_origin) {
+    opener_origin_ = opener_origin;
+  }
+
   JavaBridgeDispatcherHostManager* java_bridge_dispatcher_host_manager() const {
     return java_bridge_dispatcher_host_manager_.get();
   }
@@ -213,6 +217,7 @@ class CONTENT_EXPORT TabContents
   virtual content::WebUI::TypeID GetWebUITypeForCurrentState() OVERRIDE;
   virtual content::WebUI* GetWebUIForCurrentState() OVERRIDE;
   virtual bool GotResponseToLockMouseRequest(bool allowed) OVERRIDE;
+  virtual const GURL& GetOpenerOrigin() const OVERRIDE;
 
   // Implementation of PageNavigator.
   virtual content::WebContents* OpenURL(
@@ -649,6 +654,9 @@ class CONTENT_EXPORT TabContents
   // Our view type. Default is VIEW_TYPE_TAB_CONTENTS.
   content::ViewType view_type_;
 
+  // The origin of the opener.

[Charlie Reis, 2012/03/01 19:06:03]

I don't quite follow this.  The origin of the opener can change if it navigates.
 How long is this valid?  If you only care about it for the initial value, maybe
we should be clearer in the name, like initial_opener_origin_ (though I'm not
sure what that's useful for).

[cbentzel, 2012/03/01 22:18:53]

I thought opener was associated with a browsing context, rather than an
individual navigation within the context?

This is probably incorrect either way. I'll rethink how to do this.

[Charlie Reis, 2012/03/01 22:24:38]

Correct.  The opener is a browser context, like a tab or a frame.  It stays
valid as the page within it (and thus the origin) changes.  That's why I don't
think it makes sense to remember the origin of the opener's current page.

+  GURL opener_origin_;
+
   DISALLOW_COPY_AND_ASSIGN(TabContents);
 };