Add desktop engagement metrics.

chrome/browser/metrics/desktop_engagement/chrome_visibility_observer_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/chrome_visibility_observer.h"
+
+#include "base/memory/singleton.h"
+#include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_list.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/test/test_utils.h"
+
+// Mock class for |ChromeVisibilityObserver| for testing.
+class MockChromeVisibilityObserver : public metrics::ChromeVisibilityObserver {
+ public:
+  MockChromeVisibilityObserver() : is_active_(false) {}
+
+  bool IsActive() { return is_active_; }

[Alexei Svitkine (slow), 2016/07/26 22:00:40]

bool is_active() const

Same for other accessors in your tests.

[gayane -on leave until 09-2017, 2016/07/27 21:10:25]

Done.

+
+ private:
+  void SendVisibilityChangeEvent(bool active) override { is_active_ = active; }
+
+  bool is_active_;

[Alexei Svitkine (slow), 2016/07/26 22:00:40]

Add an empty line below this.

[gayane -on leave until 09-2017, 2016/07/27 21:10:24]

Done.

+  DISALLOW_COPY_AND_ASSIGN(MockChromeVisibilityObserver);
+};
+
+class ChromeVisibilityObserverBrowserTest : public InProcessBrowserTest {};
+
+IN_PROC_BROWSER_TEST_F(ChromeVisibilityObserverBrowserTest, VisibilityTest) {
+  MockChromeVisibilityObserver observer;
+
+  EXPECT_FALSE(observer.IsActive());
+  Browser* new_browser = CreateBrowser(browser()->profile());
+  EXPECT_TRUE(observer.IsActive());
+
+  Browser* incognito_browser = CreateIncognitoBrowser();
+  EXPECT_TRUE(observer.IsActive());
+
+  CloseBrowserSynchronously(incognito_browser);
+  EXPECT_TRUE(observer.IsActive());
+
+  CloseBrowserSynchronously(new_browser);
+  CloseBrowserSynchronously(browser());
+  EXPECT_FALSE(observer.IsActive());
+}