Move the logic to set up a local origin for shell run to shell_arguments.py.

mojo/devtools/common/devtoolslib/shell_arguments.py

 # Copyright 2015 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.
 
 """Functions that configure the shell before it is run manipulating its argument
 list."""
 
 import urlparse
 
+_LOCAL_ORIGIN_PORT = 31337
+
 _MAP_ORIGIN_PREFIX = '--map-origin='
 # When spinning up servers for local origins, we want to use predictable ports
 # so that caching works between subsequent runs with the same command line.
 _MAP_ORIGIN_BASE_PORT = 31338
 
 # Port on which the mojo:debugger http server will be available on the host
 # machine.
 _MOJO_DEBUGGER_PORT = 7777
 
 
@@ skipping 52 matching lines @@
 def ConfigureDebugger(shell):
   """Configures mojo:debugger to run and sets up port forwarding for its http
   server if the shell is running on a device.
 
   Returns:
     Arguments that need to be appended to the shell argument list in order to
     run with the debugger.
   """
   shell.ForwardHostPortToShell(_MOJO_DEBUGGER_PORT)
   return ['mojo:debugger %d' % _MOJO_DEBUGGER_PORT]
+
+
+def ConfigureLocalOrigin(shell, local_dir, fixed_port=True):
+  """Sets up a local http server to serve files in |local_dir| along with
+  device port forwarding if needed.
+
+  Returns:
+    The list of arguments to be appended to the shell argument list.
+  """
+
+  origin_url = shell.ServeLocalDirectory(
+      local_dir, _LOCAL_ORIGIN_PORT if fixed_port else 0)
+  return ["--origin=" + origin_url]