Add support for HTTP handlers that are in self-contained apps. Also add an example app.

services/http_server/public/http_server.mojom

 // 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.
 
 module mojo;
 
-// TODO(jam): interface for http_server
+import "services/http_server/public/http_request.mojom";
+import "services/http_server/public/http_response.mojom";
+
+[Client=HttpServerClient]
+interface HttpServerService {
+  // Add a handler for the given regex path.
+  AddHandler(string path) => (bool success);
+
+  // Remove a previously registered handler.
+  RemoveHandler(string path) => (bool success);
+};
+
+interface HttpServerClient {
+  OnHandleRequest(HttpRequest request) => (HttpResponse response);
+};