Add metrics to keep track of the tab activate/deactivate cycle

chrome/browser/metrics/tab_reactivation_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/tab_reactivation_tracker.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/common/url_constants.h"
+#include "chrome/test/base/in_process_browser_test.h"
+
+namespace metrics {
+
+// Simple test fixture that just counts the notification received by a
+// TabReactivationTracker.
+class TabReactivationTrackerTest : public InProcessBrowserTest,
+                                   public TabReactivationTracker::Delegate {
+ public:
+  TabReactivationTrackerTest()
+      : tab_reactivation_count_(0), tab_deactivation_count_(0) {}
+
+  // TabReactivationTracker::Delegate:
+  void OnTabReactivated(content::WebContents* contents) override;
+  void OnTabDeactivated(content::WebContents* contents) override;
+
+  int tab_reactivation_count() { return tab_reactivation_count_; }
+  int tab_deactivation_count() { return tab_deactivation_count_; }
+
+ private:
+  int tab_reactivation_count_;
+  int tab_deactivation_count_;
+};
+
+void TabReactivationTrackerTest::OnTabReactivated(
+    content::WebContents* contents) {
+  tab_reactivation_count_++;
+}
+
+void TabReactivationTrackerTest::OnTabDeactivated(
+    content::WebContents* contents) {
+  tab_deactivation_count_++;
+}
+
+IN_PROC_BROWSER_TEST_F(TabReactivationTrackerTest, CorrectTracking) {
+  content::OpenURLParams open1(
+      GURL(chrome::kChromeUIAboutURL), content::Referrer(),
+      WindowOpenDisposition::CURRENT_TAB, ui::PAGE_TRANSITION_TYPED, false);
+
+  content::OpenURLParams open2(GURL(chrome::kChromeUIAboutURL),
+                               content::Referrer(),
+                               WindowOpenDisposition::NEW_FOREGROUND_TAB,
+                               ui::PAGE_TRANSITION_TYPED, false);
+
+  TabReactivationTracker tab_reactivation_tracker(this);
+
+  EXPECT_EQ(0, tab_reactivation_count());
+  EXPECT_EQ(0, tab_deactivation_count());
+
+  // Open one tab.
+  browser()->OpenURL(open1);
+  ASSERT_EQ(1, browser()->tab_strip_model()->count());
+  EXPECT_EQ(0, tab_reactivation_count());
+  EXPECT_EQ(0, tab_deactivation_count());
+
+  // Open a second tab.
+  browser()->OpenURL(open2);
+  ASSERT_EQ(2, browser()->tab_strip_model()->count());
+  EXPECT_EQ(0, tab_reactivation_count());
+  EXPECT_EQ(1, tab_deactivation_count());
+
+  // Reactivate the first tab.
+  browser()->tab_strip_model()->ActivateTabAt(0, false);
+  EXPECT_EQ(1, tab_reactivation_count());
+  EXPECT_EQ(2, tab_deactivation_count());
+
+  // Closing a tab doesn't count as a deactivation.
+  browser()->tab_strip_model()->CloseWebContentsAt(1, 0);
+  ASSERT_EQ(1, browser()->tab_strip_model()->count());
+  EXPECT_EQ(1, tab_reactivation_count());
+  EXPECT_EQ(2, tab_deactivation_count());
+}
+
+}  // namespace metrics