Add desktop engagement metrics.

chrome/browser/metrics/desktop_engagement/audible_contents_tracker_browsertest.cc

+// 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.
+#include "chrome/browser/metrics/desktop_engagement/audible_contents_tracker.h"
+
+#include "base/path_service.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/test/browser_test_base.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+// Observer for testing AudibleContentsTracker.
+class MockAudibleContentsObserver
+    : public metrics::AudibleContentsTracker::Observer {
+ public:
+  MockAudibleContentsObserver() {}
+
+  // Initializes tracker/observer pair.
+  static void Initialize() {
+    DCHECK(!tracker_);
+    DCHECK(!observer_);
+    observer_ = new MockAudibleContentsObserver();
+    tracker_ = new metrics::AudibleContentsTracker(observer_);
+  }
+
+  static MockAudibleContentsObserver* GetInstance() { return observer_; }
+
+  // AudibleContentsTracker::Observer:
+  void OnAudioStart() override { is_audio_playing_ = true; }
+  void OnAudioEnd() override { is_audio_playing_ = false; }
+
+  bool IsAudioPlaying() { return is_audio_playing_; }
+
+ private:
+  // Singletons for performing the tracking and observing state changes. These
+  // are deliberately leaked at shutdown.
+  static metrics::AudibleContentsTracker* tracker_;
+  static MockAudibleContentsObserver* observer_;

[chrisha, 2016/07/20 21:49:26]

Couldn't these be owned by the test fixture, and allocated/destroyed in
SetUp/TearDown? Cleaner than using singletons here, IMO.

[gayane -on leave until 09-2017, 2016/07/22 18:44:09]

Done.

+
+  bool is_audio_playing_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(MockAudibleContentsObserver);
+};
+
+metrics::AudibleContentsTracker* MockAudibleContentsObserver::tracker_ =
+    nullptr;
+MockAudibleContentsObserver* MockAudibleContentsObserver::observer_ = nullptr;
+
+}  // namespace
+
+class AudibleContentsTrackerTest : public InProcessBrowserTest {};
+
+IN_PROC_BROWSER_TEST_F(AudibleContentsTrackerTest, test) {
+  MockAudibleContentsObserver::Initialize();
+  MockAudibleContentsObserver* observer =
+      MockAudibleContentsObserver::GetInstance();
+  EXPECT_FALSE(observer->IsAudioPlaying());
+
+  // For serving audio.
+  ASSERT_TRUE(embedded_test_server()->Start());
+  base::FilePath test_data_dir;
+  ASSERT_TRUE(PathService::Get(base::DIR_SOURCE_ROOT, &test_data_dir));
+  embedded_test_server()->ServeFilesFromDirectory(
+      test_data_dir.AppendASCII("chrome/test/data/"));
+  ui_test_utils::NavigateToURL(
+      browser(), embedded_test_server()->GetURL("/autoplay_audio.html"));
+
+  // Wait until the audio starts.
+  while (!observer->IsAudioPlaying()) {
+    base::RunLoop().RunUntilIdle();
+  }
+
+  // Wait until the audio stops.
+  while (observer->IsAudioPlaying()) {
+    base::RunLoop().RunUntilIdle();
+  }
+}