mojo: make NetworkServiceImpl clean up after itself

mojo/services/network/main.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 "base/at_exit.h"
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
@@ skipping 25 matching lines @@
   scoped_ptr<mojo::NetworkContext> context_;
 };
 
 extern "C" APPLICATION_EXPORT MojoResult CDECL MojoMain(
     MojoHandle shell_handle) {
   base::CommandLine::Init(0, NULL);
 #if !defined(COMPONENT_BUILD)
   base::AtExitManager at_exit;
 #endif
 
-  // The IO message loop allows us to use net::URLRequest on this thread.
-  base::MessageLoopForIO loop;
+  // The Delegate owns the NetworkContext, which needs to outlive
+  // MessageLoopForIO. Destruction of the message loop will serve to
+  // invalidate connections made to network services (URLLoader) and cause
+  // the service instances to be cleaned up as a result of observing pipe
+  // errors. This is important as ~URLRequestContext asserts that no out-
+  // standing URLRequests exist.
+  Delegate delegate;
+  {
+    // The IO message loop allows us to use net::URLRequest on this thread.
+    base::MessageLoopForIO loop;
 
-  Delegate delegate;
-  mojo::ApplicationImpl app(
-      &delegate, mojo::MakeScopedHandle(mojo::MessagePipeHandle(shell_handle)));
+    mojo::ApplicationImpl app(
+        &delegate,
+        mojo::MakeScopedHandle(mojo::MessagePipeHandle(shell_handle)));
 
-  loop.Run();
+    loop.Run();
+  }
   return MOJO_RESULT_OK;
 }