For the out-of-process NativeRunner, make sure that Start()'s callback always gets called.

shell/app_child_process_host.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 "shell/app_child_process_host.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "mojo/edk/embedder/embedder.h"
@@ skipping 33 matching lines @@
 void AppChildProcessHost::WillStart() {
   DCHECK(platform_channel()->is_valid());
 
   ScopedMessagePipeHandle handle(embedder::CreateChannel(
       platform_channel()->Pass(), context()->task_runners()->io_runner(),
       base::Bind(&AppChildProcessHost::DidCreateChannel,
                  base::Unretained(this)),
       base::MessageLoop::current()->message_loop_proxy()));
 
   controller_.Bind(handle.Pass());
+  controller_.set_error_handler(this);
 }
 
 void AppChildProcessHost::DidStart(bool success) {
   DVLOG(2) << "AppChildProcessHost::DidStart()";
 
   if (!success) {
     LOG(ERROR) << "Failed to start app child process";
     AppCompleted(MOJO_RESULT_UNKNOWN);
     return;
   }
 }
 
+void AppChildProcessHost::OnConnectionError() {
+  AppCompleted(MOJO_RESULT_UNKNOWN);
+}
+
 // Callback for |embedder::CreateChannel()|.
 void AppChildProcessHost::DidCreateChannel(
     embedder::ChannelInfo* channel_info) {
   DVLOG(2) << "AppChildProcessHost::DidCreateChannel()";
 
   CHECK(channel_info);
   channel_info_ = channel_info;
 }
 
 void AppChildProcessHost::AppCompleted(int32_t result) {
   if (!on_app_complete_.is_null()) {
     auto on_app_complete = on_app_complete_;
     on_app_complete_.reset();
     on_app_complete.Run(result);
   }
 }
 
 }  // namespace shell
 }  // namespace mojo