PlzNavigate: Avoid duplicate SiteInstance creation during navigation.

content/browser/frame_host/render_frame_host_manager.h

 // Copyright 2013 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 CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_MANAGER_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_MANAGER_H_
 
 #include <list>
 
 #include "base/basictypes.h"
@@ skipping 470 matching lines @@
   // This is a helper function for GetSiteInstanceForNavigation.
   SiteInstance* GetSiteInstanceForURL(const GURL& dest_url,
                                       SiteInstance* source_instance,
                                       SiteInstance* current_instance,
                                       SiteInstance* dest_instance,
                                       ui::PageTransition transition,
                                       bool dest_is_restore,
                                       bool dest_is_view_source_mode,
                                       bool force_browsing_instance_swap);
 
+  // Creates a new SiteInstance for the provided URL under a new browsing
+  // instance.
+  // PlzNavigate: If a SiteInstance was already previously created for this URL
+  // for the same navigation, return that one. Otherwise create a new one and
+  // return it.
+  SiteInstance* CreateSiteInstanceForURL(BrowserContext* browser_context,
+                                         const GURL& dest_url);
+
   // Determines the appropriate url to use as the current url for SiteInstance
   // selection.
   const GURL& GetCurrentURLForSiteInstance(
       SiteInstance* current_instance,
       NavigationEntry* current_entry);
 
   // Creates a new RenderFrameHostImpl for the |new_instance| and assign it to
   // |pending_render_frame_host_| while respecting the opener route if needed
   // and stores it in pending_render_frame_host_.
   void CreatePendingRenderFrameHost(SiteInstance* old_instance,
@@ skipping 187 matching lines @@
   bool should_reuse_web_ui_;
 
   base::WeakPtrFactory<RenderFrameHostManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_MANAGER_H_