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

chrome/browser/metrics/tab_usage_recorder.h

Index: chrome/browser/metrics/tab_usage_recorder.h
diff --git a/chrome/browser/metrics/tab_usage_recorder.h b/chrome/browser/metrics/tab_usage_recorder.h
new file mode 100644
index 0000000000000000000000000000000000000000..d3eca89ef7bc4095325a7c3ede952b0e4884212a
--- /dev/null
+++ b/chrome/browser/metrics/tab_usage_recorder.h
@@ -0,0 +1,39 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.

[Georges Khalil, 2016/09/14 16:10:17]

nit: 2016.

[Patrick Monette, 2016/09/16 00:14:00]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_
+#define CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_
+
+#include <map>
+#include <memory>
+
+#include "chrome/browser/ui/browser_list_observer.h"
+
+namespace metrics {
+
+// This class is used to record metrics about tab reactivation. Specifically,
+// it records the number of time a tab is deactivated and reactivated. The

[Georges Khalil, 2016/09/14 16:10:17]

nit: s/time/times.

[Patrick Monette, 2016/09/16 00:14:00]

Done.

+// ratio of both can be calculated for tabs with different properties (e.g. If
+// the tab is pinned to the tab strip) to see if they are correlated with higher
+// probability of tab reactivation.
+class TabUsageRecorder : public chrome::BrowserListObserver {
+ public:
+  static void Initialize();
+
+  TabUsageRecorder();

[Georges Khalil, 2016/09/14 16:10:17]

Make this private?

[Patrick Monette, 2016/09/16 00:14:00]

Done.

+  ~TabUsageRecorder();

[Georges Khalil, 2016/09/14 16:10:17]

Add override.

[Patrick Monette, 2016/09/16 00:14:00]

Done.

+
+  // chrome::BrowserListObserver:
+  void OnBrowserAdded(Browser* browser) override;
+  void OnBrowserRemoved(Browser* browser) override;

[Georges Khalil, 2016/09/14 16:10:17]

Use BrowserTabStripTracker instead.

[Patrick Monette, 2016/09/16 00:14:00]

Done.

I needed to change the TabStripModelObserver interface to make it work.

[Georges Khalil, 2016/09/16 18:58:35]

AFAIK, the tracker should be a drop in replacement. Why is the change to the
interface needed?

[Patrick Monette, 2016/09/19 17:47:12]

I meant adding a TabStripModel* parameter to the interface. In the last
revision, when I was doing my own tracking, I was also tracking which
TabStripModel is associated to which TabStripModelObserver (via tracking the
Browser*). This is not something that BrowserTabStripTracker does.

+
+ private:
+  class TabStripObserver;
+
+  std::map<Browser*, std::unique_ptr<TabStripObserver>> tab_strip_observer_map_;

[Georges Khalil, 2016/09/14 16:10:17]

Comment this member. I don't see its usefulness, where is it used?

[Patrick Monette, 2016/09/16 00:14:00]

No longer applicable as I removed it.

+};

[Georges Khalil, 2016/09/14 16:10:17]

Disallow copy.

[Patrick Monette, 2016/09/16 00:14:00]

Done.

+
+}  // namespace metrics
+
+#endif  // CHROME_BROWSER_METRICS_TAB_USAGE_RECORDER_H_