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_;

[nasko, 2014/01/23 23:34:58]

Why is this a multimap? There should be only one RVH per SiteInstance in a
FrameTree.

[clamy, 2014/01/24 17:01:54]

It seems that we can end up reusing the same site instanec id at least, which
can cause us to have at least one active RVH and one RVH pending shutdown for
the same site instance id (that happens in one of the browser tests). Therefore,
I was worried about corner cases where we would navigate fast enough so that we
end up with two RVH pending shutdown and sharing the same site instance id.

+
   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_