Prerendered tabs use the same SessionStorage namespace as the tab that triggered the prerender.

chrome/browser/prerender/prerender_manager.h

Index: chrome/browser/prerender/prerender_manager.h
diff --git a/chrome/browser/prerender/prerender_manager.h b/chrome/browser/prerender/prerender_manager.h
index abd1541dc3366309fcb2b930c7239cea6e598fec..8c086a1ec60cc1c0445a78ebd15201aa98ed3882 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -101,8 +101,12 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   // Adds a prerender for |url| if valid. As the prerender request is coming
   // from a source without a RenderViewHost (i.e., the omnibox) we don't have a
   // child or route id, or a referrer. This method uses sensible values for
-  // those.
-  bool AddPrerenderFromOmnibox(const GURL& url);
+  // those. The |session_storage_namespace| can be determined at this time,
+  // however, because it is based off of the destination tab rather than the
+  // current contents.

[mmenke, 2011/11/02 02:27:55]

"Destination tab rather than the current contents"?  What does that mean?

[cbentzel, 2011/11/02 15:57:08]

Fixed comment - thanks for pointing this out.

+  bool AddPrerenderFromOmnibox(
+    const GURL& url,
+    SessionStorageNamespace* session_storage_namespace);
 
   // Destroy all prerenders for the given child route id pair and assign a final
   // status to them.
@@ -245,12 +249,15 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
 
   // Adds a prerender for |url| from referrer |referrer| initiated from the
   // RenderViewHost specified by |child_route_id_pair|. The |origin| specifies
-  // how the prerender was added.
+  // how the prerender was added. If the |session_storage_namespace| is NULL,
+  // it is discovered using the RenderViewHost specified by
+  // |child_route_id_pair|.
   bool AddPrerender(
       Origin origin,
       const std::pair<int, int>& child_route_id_pair,
       const GURL& url,
-      const GURL& referrer);
+      const GURL& referrer,
+      SessionStorageNamespace* session_storage_namespace);
 
   // Adds a pending preload issued by the prerendering RenderView identified by
   // |child_route_id_pair|.  If and when that prerendering RenderView is used,
@@ -293,10 +300,12 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   void DeleteOldEntries();
   virtual base::Time GetCurrentTime() const;
   virtual base::TimeTicks GetCurrentTimeTicks() const;
-  virtual PrerenderContents* CreatePrerenderContents(const GURL& url,
-                                                     const GURL& referrer,
-                                                     Origin origin,
-                                                     uint8 experiment_id);
+  virtual PrerenderContents* CreatePrerenderContents(
+      SessionStorageNamespace* session_storage_namespace,
+      const GURL& url,
+      const GURL& referrer,
+      Origin origin,
+      uint8 experiment_id);
 
   // Checks if the PrerenderContents has been added to the pending delete list.
   bool IsPendingDelete(PrerenderContents* entry) const;