[Findit] Add findit_for_client to do analysis based on client_id

appengine/findit/common/appengine_util.py

 # Copyright 2016 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 os
 
+from google.appengine.api import app_identity
 from google.appengine.api import modules
 
 
 def IsInDevServer():  # pragma: no cover.
   """Returns whether the code runs in dev server locally."""
   return os.environ['APPLICATION_ID'].startswith('dev')
 
 
 def GetCurrentVersion():  # pragma: no cover.
   """Returns the version of this module."""
   return modules.get_current_version_name()
 
 
+def GetDefaultVersionHostname():  # pragma: no cover.
+  """Returns the default version hostname of this service."""
+  return app_identity.get_default_version_hostname()
+
+
 def GetTargetNameForModule(module_name, version=None):  # pragma: no cover.
   """Returns the target name for the given module and version.
 
   Version defaults to the one running this code.
   """
   if IsInDevServer():
     # Dev server doesn't support multiple versions of a module.
     return module_name
   else:
     version = version or GetCurrentVersion()
     return '%s.%s' % (version, module_name)