Revert of Move content's shell connections to the IO thread

content/renderer/render_thread_impl.h

 // 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.
 
 #ifndef CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 #define CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 148 matching lines @@
   void Shutdown() override;
 
   // When initializing WebKit, ensure that any schemes needed for the content
   // module are registered properly.  Static to allow sharing with tests.
   static void RegisterSchemes();
 
   // Notify V8 that the date/time configuration of the system might have
   // changed.
   static void NotifyTimezoneChange();
 
-  // ChildThreadImpl implementation:
-  void AddConnectionFilters(MojoShellConnection* connection) override;
-
   // RenderThread implementation:
   bool Send(IPC::Message* msg) override;
   IPC::SyncChannel* GetChannel() override;
   std::string GetLocale() override;
   IPC::SyncMessageFilter* GetSyncMessageFilter() override;
   scoped_refptr<base::SingleThreadTaskRunner> GetIOTaskRunner() override;
   void AddRoute(int32_t routing_id, IPC::Listener* listener) override;
   void RemoveRoute(int32_t routing_id) override;
   int GenerateRoutingID() override;
   void AddFilter(IPC::MessageFilter* filter) override;
@@ skipping 520 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
 #if defined(COMPILER_MSVC)
 #pragma warning(pop)
 #endif
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_