Enable swapping a frame back in to its parent process

content/browser/frame_host/render_frame_host_manager.cc

Index: content/browser/frame_host/render_frame_host_manager.cc
diff --git a/content/browser/frame_host/render_frame_host_manager.cc b/content/browser/frame_host/render_frame_host_manager.cc
index 19e790617f40fdcfdcf8951d6bf6db5d89a529b2..bb1bfd6f2f20f04fb818d41d53501baffda0cbd8 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -1188,13 +1188,28 @@ bool RenderFrameHostManager::InitRenderFrame(
     return true;
 
   int parent_routing_id = MSG_ROUTING_NONE;
+  int proxy_routing_id = MSG_ROUTING_NONE;
   if (frame_tree_node_->parent()) {
     parent_routing_id = frame_tree_node_->parent()->render_manager()->
         GetRoutingIdForSiteInstance(render_frame_host->GetSiteInstance());
     CHECK_NE(parent_routing_id, MSG_ROUTING_NONE);
   }
+  // Check whether there is an existing proxy for this frame in this
+  // SiteInstance. If there is, the new RenderFrame needs to be able to talk to

[Charlie Reis, 2014/10/28 20:10:10]

nit: talk to -> find

[Nate Chapin, 2014/10/30 19:00:51]

Done.

+  // the proxy it is replacing, so that it can fully intiialize itself.

[Charlie Reis, 2014/10/28 20:10:10]

nit: initialize

[Nate Chapin, 2014/10/30 19:00:51]

Done.

+  // NOTE: This is the only time that a RenderFrameProxy can be in the same

[nasko, 2014/10/28 21:58:15]

nit: Since this is code in the browser and SiteInstance is a browser side
concept, let's use the *Host version of the objects.
RenderFrameProxyHost/RenderFrameHost.

[Nate Chapin, 2014/10/30 19:00:50]

Done.

+  // SiteInstance as its RenderFrame. This is only the case until the
+  // RenderFrame commits, at which point it will replace and delete the
+  // RenderFrameProxy.
+  RenderFrameProxyHost* existing_proxy =
+      GetRenderFrameProxyHost(render_frame_host->GetSiteInstance());
+  if (existing_proxy) {
+    proxy_routing_id = existing_proxy->GetRoutingID();
+    CHECK_NE(proxy_routing_id, MSG_ROUTING_NONE);
+  }
   return delegate_->CreateRenderFrameForRenderManager(render_frame_host,
-                                                      parent_routing_id);
+                                                      parent_routing_id,
+                                                      proxy_routing_id);
 }
 
 int RenderFrameHostManager::GetRoutingIdForSiteInstance(