Have the unload event execute in background on cross-site navigations

content/browser/frame_host/frame_tree.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_FRAME_TREE_H_
 #define CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 112 matching lines @@
   // the number drops to zero, we call Shutdown on the RenderViewHost.
   void RegisterRenderFrameHost(RenderFrameHostImpl* render_frame_host);
   void UnregisterRenderFrameHost(RenderFrameHostImpl* render_frame_host);
 
   // Returns the FrameTreeNode with the given renderer-specific |frame_id|.
   // TODO(creis): Make this private and replace this with a version that takes
   // in a routing ID.
   FrameTreeNode* FindByFrameID(int64 frame_id);
 
  private:
-  typedef std::pair<RenderViewHostImpl*, int> RenderViewHostRefCount;
-  typedef base::hash_map<int, RenderViewHostRefCount> RenderViewHostMap;
+  typedef base::hash_map<int, RenderViewHostImpl*> RenderViewHostMap;
+  typedef std::multimap<int, RenderViewHostImpl*> RenderViewHostMultiMap;
 
   // These delegates are installed into all the RenderViewHosts and
   // RenderFrameHosts that we create.
   RenderFrameHostDelegate* render_frame_delegate_;
   RenderViewHostDelegate* render_view_delegate_;
   RenderWidgetHostDelegate* render_widget_delegate_;
   RenderFrameHostManager::Delegate* manager_delegate_;
 
-  // Map of SiteInstance ID to a (RenderViewHost, refcount) pair.  This allows
-  // us to look up the RenderViewHost for a given SiteInstance when creating
-  // RenderFrameHosts, and it allows us to call Shutdown on the RenderViewHost
-  // and remove it from the map when no more RenderFrameHosts are using it.
+  // Map of SiteInstance ID to a RenderViewHost.  This allows us to look up the
+  // RenderViewHost for a given SiteInstance when creating RenderFrameHosts, and
+  // it allows us to call Shutdown on the RenderViewHost and remove it from the
+  // map when no more RenderFrameHosts are using it.
   //
   // Must be declared before |root_| so that it is deleted afterward.  Otherwise
   // the map will be cleared before we delete the RenderFrameHosts in the tree.
   RenderViewHostMap render_view_host_map_;
 
+  // Map of SiteInstance ID to RenderViewHosts that are pending shutdown.
+  RenderViewHostMultiMap render_view_host_pending_shutdown_map_;
+
   scoped_ptr<FrameTreeNode> root_;
 
   base::Callback<void(RenderViewHostImpl*, int64)> on_frame_removed_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameTree);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_FRAME_TREE_H_