Don't swap out the old RenderFrameHost until the new one commits.

content/renderer/render_frame_impl.cc

 // 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.
 
 #include "content/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 982 matching lines @@
 
 void RenderFrameImpl::OnSwapOut(int proxy_routing_id) {
   RenderFrameProxy* proxy = NULL;
   bool is_site_per_process =
       CommandLine::ForCurrentProcess()->HasSwitch(switches::kSitePerProcess);
 
   // Only run unload if we're not swapped out yet, but send the ack either way.
   if (!is_swapped_out_ || !render_view_->is_swapped_out_) {
     // Swap this RenderFrame out so the frame can navigate to a page rendered by
     // a different process.  This involves running the unload handler and
-    // clearing the page.  Once WasSwappedOut is called, we also allow this
-    // process to exit if there are no other active RenderFrames in it.
+    // clearing the page.  We also allow this process to exit if there are no
+    // other active RenderFrames in it.
 
     // Send an UpdateState message before we get swapped out. Create the
     // RenderFrameProxy as well so its routing id is registered for receiving
     // IPC messages.
     render_view_->SyncNavigationState();
     proxy = RenderFrameProxy::CreateProxyToReplaceFrame(this,
                                                         proxy_routing_id);
 
     // Synchronously run the unload handler before sending the ACK.
     // TODO(creis): Call dispatchUnloadEvent unconditionally here to support
@@ skipping 52 matching lines @@
     if (frame_->parent()) {
       frame_->swap(proxy->web_frame());
       if (is_site_per_process) {
         // TODO(nasko): delete the frame here, since we've replaced it with a
         // proxy.
       }
     } else {
       set_render_frame_proxy(proxy);
     }
   }
+
+  // Safe to exit if no one else is using the process.
+  if (!frame_->parent())
+    render_view_->WasSwappedOut();
 }
 
 void RenderFrameImpl::OnContextMenuClosed(
     const CustomContextMenuContext& custom_context) {
   if (custom_context.request_id) {
     // External request, should be in our map.
     ContextMenuClient* client =
         pending_context_menus_.Lookup(custom_context.request_id);
     if (client) {
       client->OnMenuClosed(custom_context.request_id);
@@ skipping 2632 matching lines @@
 
 #if defined(ENABLE_BROWSER_CDMS)
 RendererCdmManager* RenderFrameImpl::GetCdmManager() {
   if (!cdm_manager_)
     cdm_manager_ = new RendererCdmManager(this);
   return cdm_manager_;
 }
 #endif  // defined(ENABLE_BROWSER_CDMS)
 
 }  // namespace content