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

shell/app_child_process_host.cc

Index: shell/app_child_process_host.cc
diff --git a/shell/app_child_process_host.cc b/shell/app_child_process_host.cc
index 3f97b5ee1d0349a75a4afd399993768332f9b4e5..6cdcfaa206602704ce6861f6a473316823eb7104 100644
--- a/shell/app_child_process_host.cc
+++ b/shell/app_child_process_host.cc
@@ -51,6 +51,7 @@ void AppChildProcessHost::WillStart() {
       base::MessageLoop::current()->message_loop_proxy()));
 
   controller_.Bind(handle.Pass());
+  controller_.set_error_handler(this);
 }
 
 void AppChildProcessHost::DidStart(bool success) {
@@ -63,6 +64,10 @@ void AppChildProcessHost::DidStart(bool success) {
   }
 }
 
+void AppChildProcessHost::OnConnectionError() {
+  AppCompleted(MOJO_RESULT_UNKNOWN);
+}
+
 // Callback for |embedder::CreateChannel()|.
 void AppChildProcessHost::DidCreateChannel(
     embedder::ChannelInfo* channel_info) {