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

content/browser/frame_host/frame_tree.cc

Index: content/browser/frame_host/frame_tree.cc
diff --git a/content/browser/frame_host/frame_tree.cc b/content/browser/frame_host/frame_tree.cc
index f26c46c02360a0eda43722ffe1a1d417709e857a..bec42bec7be8f156037bf5c73af55efcd795db14 100644
--- a/content/browser/frame_host/frame_tree.cc
+++ b/content/browser/frame_host/frame_tree.cc
@@ -178,7 +178,17 @@ RenderViewHostImpl* FrameTree::CreateRenderViewHostForMainFrame(
   DCHECK(main_frame_routing_id != MSG_ROUTING_NONE);
   RenderViewHostMap::iterator iter =
       render_view_host_map_.find(site_instance->GetId());
-  CHECK(iter == render_view_host_map_.end());
+  if (iter != render_view_host_map_.end()) {
+    // If a RenderViewHost is pending shutdown for this |site_instance|, put it
+    // in the map of RenderViewHost pending shutdown. Otherwise there should not
+    // be a RenderViewHost for the site instance.
+    CHECK_EQ(RenderViewHostImpl::STATE_PENDING_SHUTDOWN,
+             iter->second->rvh_state());
+    render_view_host_pending_shutdown_map_.insert(
+        std::pair<int, RenderViewHostImpl*>(site_instance->GetId(),
+                                            iter->second));
+    render_view_host_map_.erase(iter);
+  }
   RenderViewHostImpl* rvh = static_cast<RenderViewHostImpl*>(
       RenderViewHostFactory::Create(site_instance,
                                     render_view_delegate_,
@@ -188,8 +198,7 @@ RenderViewHostImpl* FrameTree::CreateRenderViewHostForMainFrame(
                                     swapped_out,
                                     hidden));
 
-  render_view_host_map_[site_instance->GetId()] =
-      RenderViewHostRefCount(rvh, 0);
+  render_view_host_map_[site_instance->GetId()] = rvh;
   return rvh;
 }
 
@@ -200,8 +209,7 @@ RenderViewHostImpl* FrameTree::GetRenderViewHostForSubFrame(
   // TODO(creis): Mirror the frame tree so this check can't fail.
   if (iter == render_view_host_map_.end())
     return NULL;
-  RenderViewHostRefCount rvh_refcount = iter->second;
-  return rvh_refcount.first;
+  return iter->second;
 }
 
 void FrameTree::RegisterRenderFrameHost(
@@ -212,26 +220,50 @@ void FrameTree::RegisterRenderFrameHost(
       render_view_host_map_.find(site_instance->GetId());
   CHECK(iter != render_view_host_map_.end());
 
-  // Increment the refcount.
-  CHECK_GE(iter->second.second, 0);
-  iter->second.second++;
+  iter->second->increment_ref_count();
 }
 
 void FrameTree::UnregisterRenderFrameHost(
     RenderFrameHostImpl* render_frame_host) {
   SiteInstance* site_instance =
       render_frame_host->render_view_host()->GetSiteInstance();
+  int32 site_instance_id = site_instance->GetId();
   RenderViewHostMap::iterator iter =
-      render_view_host_map_.find(site_instance->GetId());
-  CHECK(iter != render_view_host_map_.end());
-
-  // Decrement the refcount and shutdown the RenderViewHost if no one else is
-  // using it.
-  CHECK_GT(iter->second.second, 0);
-  iter->second.second--;
-  if (iter->second.second == 0) {
-    iter->second.first->Shutdown();
-    render_view_host_map_.erase(iter);
+      render_view_host_map_.find(site_instance_id);
+  if (iter != render_view_host_map_.end() &&
+      iter->second == render_frame_host->render_view_host()) {
+    // Decrement the refcount and shutdown the RenderViewHost if no one else is
+    // using it.
+    CHECK_GT(iter->second->ref_count(), 0);
+    iter->second->decrement_ref_count();
+    if (iter->second->ref_count() == 0) {
+      iter->second->Shutdown();
+      render_view_host_map_.erase(iter);
+    }
+  } else {
+    // The RenderViewHost should be in the list of RenderViewHosts pending
+    // shutdown.
+    bool render_view_host_found = false;
+    std::pair<RenderViewHostMultiMap::iterator,
+              RenderViewHostMultiMap::iterator> result =
+        render_view_host_pending_shutdown_map_.equal_range(site_instance_id);
+    for (RenderViewHostMultiMap::iterator multi_iter = result.first;
+         multi_iter != result.second;
+         ++multi_iter) {
+      if (multi_iter->second != render_frame_host->render_view_host())
+        continue;
+      render_view_host_found = true;
+      // Decrement the refcount and shutdown the RenderViewHost if no one else
+      // is using it.
+      CHECK_GT(multi_iter->second->ref_count(), 0);
+      multi_iter->second->decrement_ref_count();
+      if (multi_iter->second->ref_count() == 0) {
+        multi_iter->second->Shutdown();
+        render_view_host_pending_shutdown_map_.erase(multi_iter);
+      }
+      break;
+    }
+    CHECK(render_view_host_found);
   }
 }