Prevent the browser process from creating duplicate RenderViewHosts.

content/browser/renderer_host/render_widget_host_impl.cc

 // Copyright (c) 2012 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/browser/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 #include <set>
 #include <utility>
 
@@ skipping 194 matching lines @@
     // problem, for example by tracking in the RenderWidgetHelper the routing id
     // (and surface id) that have been created, but whose RWH haven't yet.
     surface_id_ = GpuSurfaceTracker::Get()->LookupSurfaceForRenderer(
         process_->GetID(),
         routing_id_);
     DCHECK(surface_id_);
   }
 
   is_threaded_compositing_enabled_ = IsThreadedCompositingEnabled();
 
-
-  g_routing_id_widget_map.Get().insert(std::make_pair(
-      RenderWidgetHostID(process->GetID(), routing_id_), this));
+  std::pair<RoutingIDWidgetMap::iterator, bool> result =
+      g_routing_id_widget_map.Get().insert(std::make_pair(
+          RenderWidgetHostID(process->GetID(), routing_id_), this));
+  CHECK(result.second) << "Inserting a duplicate item!";
   process_->AddRoute(routing_id_, this);
 
   // If we're initially visible, tell the process host that we're alive.
   // Otherwise we'll notify the process host when we are first shown.
   if (!hidden)
     process_->WidgetRestored();
 
   accessibility_mode_ =
       BrowserAccessibilityStateImpl::GetInstance()->accessibility_mode();
 
@@ skipping 2256 matching lines @@
         continue;
       }
       RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(rwh);
       if (rwhi_set.insert(rwhi).second)
         rwhi->FrameSwapped(latency_info);
     }
   }
 }
 
 }  // namespace content