(NOT READY FOR REVIEW) Introduce MessagePortBypassFilter.

content/child/child_thread.h

Index: content/child/child_thread.h
diff --git a/content/child/child_thread.h b/content/child/child_thread.h
index 233e9c8cf1a0e32133e15bc24d695293e6492ebd..4b32114cb1893bb826f5018448bfeabb53257c5a 100644
--- a/content/child/child_thread.h
+++ b/content/child/child_thread.h
@@ -15,6 +15,7 @@
 #include "base/tracked_objects.h"
 #include "content/common/content_export.h"
 #include "content/common/message_router.h"
+#include "ipc/ipc_channel_proxy.h"
 #include "ipc/ipc_message.h"  // For IPC_MESSAGE_LOG_ENABLED.
 #include "webkit/child/resource_loader_bridge.h"
 
@@ -49,6 +50,28 @@ class SocketStreamDispatcher;
 class ThreadSafeSender;
 class WebSocketDispatcher;
 
+class MessagePortBypassFilter : public IPC::ChannelProxy::MessageFilter {
+ public:
+  MessagePortBypassFilter(base::SingleThreadTaskRunner* ipc_task_runner);
+  virtual ~MessagePortBypassFilter();
+
+  // IPC::ChannelProxy::MessageFilter implementation.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+  virtual bool GetSupportedMessageClasses(
+      std::vector<uint32>* supported_message_classes) const OVERRIDE;
+
+  void AddRoute(int32 routing_id, IPC::Listener* listener);
+  void RemoveRoute(int32 routing_id, const base::Closure& callback);
+
+ private:
+  void AddRouteOnIO(int32 routing_id, IPC::Listener* listener);
+  void RemoveRouteOnIO(int32 routing_id, const base::Closure& callback);
+
+  IDMap<IPC::Listener> routes_;
+  scoped_refptr<base::SingleThreadTaskRunner> ipc_task_runner_;
+  scoped_refptr<base::MessageLoopProxy> child_thread_loop_;
+};
+
 // The main thread of a child process derives from this class.
 class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
  public:
@@ -119,6 +142,10 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
     return sync_message_filter_.get();
   }
 
+  MessagePortBypassFilter* message_port_bypass_filter() const {
+    return message_port_bypass_filter_.get();
+  }
+
   // The getter should only be called on the main thread, however the
   // IPC::Sender it returns may be safely called on any thread including
   // the main thread.
@@ -232,6 +259,8 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
 
   scoped_refptr<QuotaMessageFilter> quota_message_filter_;
 
+  scoped_refptr<MessagePortBypassFilter> message_port_bypass_filter_;
+
   scoped_ptr<ChildSharedBitmapManager> shared_bitmap_manager_;
 
   base::WeakPtrFactory<ChildThread> channel_connected_factory_;