Get mojo_shell building inside chromium checkout.

mojo/public/mojo_application.gni

 # 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.
 
 import("//build/module_args/mojo.gni")
 import("mojo.gni")
 import("mojo_sdk.gni")
 
 # Generate a binary mojo application.The parameters of this template are those
 # of a shared library.
@@ skipping 334 matching lines @@
       rebase_input = rebase_path(input, root_build_dir)
       rebase_output = rebase_path(output, root_build_dir)
       args = [
         "--input=$rebase_input",
         "--output=$rebase_output",
         "--line=#!mojo mojo:android_handler",
       ]
     }
   }
 }