Always use ChannelMojo for content child processes.

content/browser/renderer_host/render_process_host_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_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 289 matching lines @@
  private:
   friend class ChildProcessLauncherBrowserTest_ChildSpawnFail_Test;
   friend class VisitRelayingRenderProcessHost;
   class ConnectionFilterController;
   class ConnectionFilterImpl;
 
   size_t worker_ref_count() {
     return service_worker_ref_count_ + shared_worker_ref_count_;
   }
 
-  std::unique_ptr<IPC::ChannelProxy> CreateChannelProxy(
-      const std::string& channel_id);
+  std::unique_ptr<IPC::ChannelProxy> CreateChannelProxy();
 
   // Creates and adds the IO thread message filters.
   void CreateMessageFilters();
 
   // Registers Mojo interfaces to be exposed to the renderer.
   void RegisterMojoInterfaces();
 
   // mojom::RouteProvider:
   void GetRoute(
       int32_t routing_id,
@@ skipping 261 matching lines @@
       instance_weak_factory_;
 
   base::WeakPtrFactory<RenderProcessHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_