Update prerender policy for custom tabs

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 fdf874e3d3f8f5b0652c30b48241c0ba4c2f23fa..e8d857496dc3db9b70ea02cd3fedb44eaca1c25d 100644
--- a/chrome/browser/prerender/prerender_manager.h
+++ b/chrome/browser/prerender/prerender_manager.h
@@ -132,7 +132,8 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
       const GURL& url,
       const content::Referrer& referrer,
       content::SessionStorageNamespace* session_storage_namespace,
-      const gfx::Size& size);
+      const gfx::Size& size,
+      bool prerender_on_mobile);
 
   // Adds a prerender for Instant Search |url| if valid. The
   // |session_storage_namespace| matches the namespace of the active tab at the
@@ -395,6 +396,11 @@ class PrerenderManager : public base::SupportsWeakPtr<PrerenderManager>,
   // disabled.
   chrome_browser_net::NetworkPredictionStatus GetPredictionStatus() const;
 
+  // Returns whether prerendering is currently enabled or the reason why it is
+  // disabled after taking into account the origin of the request.
+  chrome_browser_net::NetworkPredictionStatus GetPredictionStatusForOrigin(
+      Origin origin) const;
+
   // Adds a prerender for |url| from |referrer|. The |origin| specifies how the
   // prerender was added. If |size| is empty, then
   // PrerenderContents::StartPrerendering will instead use a default from