Add RoutingIDIssuer to ensure the correctness of ID to be routed.

content/browser/renderer_host/render_widget_helper.h

Index: content/browser/renderer_host/render_widget_helper.h
diff --git a/content/browser/renderer_host/render_widget_helper.h b/content/browser/renderer_host/render_widget_helper.h
index 98b3ca6cdb8aab356835d9026984bba7ed5c6667..4e09bdf98e83057f3e153d059749c219ac082d61 100644
--- a/content/browser/renderer_host/render_widget_helper.h
+++ b/content/browser/renderer_host/render_widget_helper.h
@@ -7,9 +7,9 @@
 
 #include <map>
 
-#include "base/atomic_sequence_num.h"
 #include "base/containers/hash_tables.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/process/process.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
@@ -33,6 +33,7 @@ struct ViewMsg_SwapOut_Params;
 namespace content {
 class GpuProcessHost;
 class ResourceDispatcherHostImpl;
+class RoutingIDIssuer;
 class SessionStorageNamespace;
 
 // Instantiated per RenderProcessHost to provide various optimizations on
@@ -80,6 +81,9 @@ class RenderWidgetHelper
 
   // Gets the next available routing id.  This is thread safe.
   int GetNextRoutingID();
+  // Probablistically verify if the ID is issued by this helper.
+  // Thread safe.
+  bool IsRoutingIDProbablyValid(int routing_id) const;
 
   // IO THREAD ONLY -----------------------------------------------------------
 
@@ -175,8 +179,7 @@ class RenderWidgetHelper
 
   int render_process_id_;
 
-  // The next routing id to use.
-  base::AtomicSequenceNumber next_routing_id_;
+  scoped_ptr<RoutingIDIssuer> routing_id_issuer_;
 
   ResourceDispatcherHostImpl* resource_dispatcher_host_;