Added metrics to track the time between task switches done via Alt+Tab and Alt+Shift+Tab.

ash/metrics/user_metrics_recorder.h

 // Copyright 2013 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.
 
 #ifndef ASH_METRICS_USER_METRICS_RECORDER_H_
 #define ASH_METRICS_USER_METRICS_RECORDER_H_
 
 #include "ash/ash_export.h"
 #include "ash/metrics/task_switch_metrics_recorder.h"
 #include "base/timer/timer.h"
@@ skipping 127 matching lines @@
  public:
   // Creates a UserMetricsRecorder that records metrics periodically. Equivalent
   // to calling UserMetricsRecorder(true).
   UserMetricsRecorder();
 
   virtual ~UserMetricsRecorder();
 
   // Records an Ash owned user action.
   void RecordUserMetricsAction(ash::UserMetricsAction action);
 
+  TaskSwitchMetricsRecorder& task_switch_metrics_recorder() {
+    return task_switch_metrics_recorder_;
+  }
+
  private:
   friend class test::UserMetricsRecorderTestAPI;
 
   // Creates a UserMetricsRecorder and will only record periodic metrics if
   // |record_periodic_metrics| is true. This is used by tests that do not want
   // the timer to be started.
   // TODO(bruthig): Add a constructor that accepts a base::RepeatingTimer so
   // that tests can inject a test double that can be controlled by the test. The
   // missing piece is a suitable base::RepeatingTimer test double.
   explicit UserMetricsRecorder(bool record_periodic_metrics);
@@ skipping 12 matching lines @@
   base::RepeatingTimer<UserMetricsRecorder> timer_;
 
   TaskSwitchMetricsRecorder task_switch_metrics_recorder_;
 
   DISALLOW_COPY_AND_ASSIGN(UserMetricsRecorder);
 };
 
 }  // namespace ash
 
 #endif  // ASH_METRICS_USER_METRICS_RECORDER_H_