Stub in more IPC attachment brokering functionality.

ipc/mojo/ipc_channel_mojo.cc

 // Copyright 2014 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 "ipc/mojo/ipc_channel_mojo.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/lazy_instance.h"
 #include "base/thread_task_runner_handle.h"
@@ skipping 506 matching lines @@
 #else
           NOTREACHED();
 #endif  //  defined(OS_POSIX) && !defined(OS_NACL)
         break;
         case MessageAttachment::TYPE_MOJO_HANDLE: {
           mojo::ScopedHandle handle =
               static_cast<IPC::internal::MojoHandleAttachment*>(
                   attachment.get())->TakeHandle();
           handles->push_back(handle.release().value());
         } break;
-        case MessageAttachment::TYPE_WIN_HANDLE:
+        case MessageAttachment::TYPE_BROKERABLE_ATTACHMENT:
+          // Brokerable attachments are handled by the AttachmentBroker so
+          // there's no need to do anything here.
           NOTREACHED();
           break;
       }
     }
 
     set->CommitAll();
   }
 
   return MOJO_RESULT_OK;
 }
@@ skipping 10 matching lines @@
     if (!ok) {
       LOG(ERROR) << "Failed to add new Mojo handle.";
       return MOJO_RESULT_UNKNOWN;
     }
   }
 
   return MOJO_RESULT_OK;
 }
 
 }  // namespace IPC