mojo: add some end-to-end shell tests and a new test sample app

mojo/services/test_service/test_request_tracker.mojom

Index: mojo/services/test_service/test_request_tracker.mojom
diff --git a/mojo/services/test_service/test_request_tracker.mojom b/mojo/services/test_service/test_request_tracker.mojom
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+// 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.test {
+
+// Various counters that services can periodically send to a
+// TestTrackedRequestService for recording.
+struct ServiceStats {
+  uint64 num_new_requests;
+  double health;
+};
+
+// A per-service summary of all the ServiceStats the
+// TestTrackedRequestService has observed.
+struct ServiceReport {
+  string service_name;
+  uint64 total_requests;
+  double mean_health;
+};
+
+// A simple interface to obtain a "report" from all services that have
+// opted to connect themselves to for request tracking.
+interface TestTrackedRequestService {
+  GetReport() => (ServiceReport[] report);
+};
+
+// TestRequestTracker records ServiceStats for an individual service
+// connection for aggregation in a TestTrackedRequestService.
+[Client=TestRequestTrackerClient]
+interface TestRequestTracker {
+  // Upload a ServiceStats for tracking.
+  RecordStats(uint64 client_id, ServiceStats stats);
+};
+
+// The client-side contract for uploading ServiceStats to TestRequestTracker.
+interface TestRequestTrackerClient {
+  const uint64 kInvalidId = 0;
+  // Handshake to tell the client its global identifier and get the name.
+  SetIdAndReturnName(uint64 id) => (string service_name);
+};
+
+}  // module mojo.test