Have mojo_shell run in its custom thread on android.

mojo/shell/keep_alive.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 "mojo/shell/keep_alive.h"
 
 #include "base/bind.h"
 #include "mojo/shell/context.h"
 
 namespace mojo {
 namespace shell {
 
 KeepAlive::KeepAlive(Context* context) : context_(context) {
-  DCHECK(context_->task_runners()->ui_runner()->RunsTasksOnCurrentThread());
+  DCHECK(context_->task_runners()->shell_runner()->RunsTasksOnCurrentThread());
   ++context_->keep_alive_counter()->count_;
 }
 
 KeepAlive::~KeepAlive() {
-  DCHECK(context_->task_runners()->ui_runner()->RunsTasksOnCurrentThread());
+  DCHECK(context_->task_runners()->shell_runner()->RunsTasksOnCurrentThread());
   if (--context_->keep_alive_counter()->count_ == 0) {
     base::MessageLoop::current()->PostTask(
         FROM_HERE,
         base::Bind(&KeepAlive::MaybeQuit, context_));
   }
 }
 
 // static
 void KeepAlive::MaybeQuit(Context* context) {
   if (context->keep_alive_counter()->count_ == 0)
     base::MessageLoop::current()->Quit();
 }
 
 }  // namespace shell
 }  // namespace mojo