Pass the final URL an app was loaded from to the app in Initialize().

examples/python/__mojo__.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.
 
 """Example python application implementing the Echo service."""
 
 import logging
 
 import application_mojom
 import example_service_mojom
 import service_provider_mojom
 import shell_mojom
 
 import mojo_system
 
 class ApplicationImpl(application_mojom.Application):
   def __init__(self, app_request_handle):
     self._providers = []
     application_mojom.Application.manager.Bind(self, app_request_handle)
 
-  def Initialize(self, shell, args):
+  def Initialize(self, shell, url, args):
     self.shell = shell
 
   def AcceptConnection(self, requestor_url, services, exposed_services):
     # We keep a reference to ServiceProviderImpl to ensure neither it nor
     # provider gets garbage collected.
     service_provider = ServiceProviderImpl(services)
     service_provider.AddService(ExampleServiceImpl)
     services.Bind(service_provider)
     self._providers.append(service_provider)
 
@@ skipping 20 matching lines @@
 
 
 def MojoMain(app_request_handle):
   """MojoMain is the entry point for a python Mojo module."""
   loop = mojo_system.RunLoop()
 
   application = ApplicationImpl(mojo_system.Handle(app_request_handle))
   application.manager.AddOnErrorCallback(loop.Quit)
 
   loop.Run()