Record time between switching the active window from Ash overview mode

Introduce the histogram
Ash.WindowSelector.TimeBetweenActiveWindowChanges
which records the amount of time between uses
of overview mode in which the user selects a window
which was not previously active.

BUG=488180
TEST=TaskSwitchMetricsRecorderTest.VerifyTaskSwitchesFromOverviewModeAreRecorded

Review URL: https://codereview.chromium.org/1132293004

Cr-Commit-Position: refs/heads/master@{#330260}

ash/metrics/task_switch_metrics_recorder.cc

@@ -19,10 +19,15 @@ const char kTabStripHistogramName[] =
 const char kAcceleratorWindowCycleHistogramName[] =
     "Ash.WindowCycleController.TimeBetweenTaskSwitches";
 
+const char kOverviewModeHistogramName[] =
+    "Ash.WindowSelector.TimeBetweenActiveWindowChanges";
+
 // Returns the histogram name for the given |task_switch_source|.
 const char* GetHistogramName(
     TaskSwitchMetricsRecorder::TaskSwitchSource task_switch_source) {
   switch (task_switch_source) {
+    case TaskSwitchMetricsRecorder::kOverviewMode:
+      return kOverviewModeHistogramName;
     case TaskSwitchMetricsRecorder::kShelf:
       return kShelfHistogramName;
     case TaskSwitchMetricsRecorder::kTabStrip:

ash/metrics/task_switch_metrics_recorder.h

@@ -22,6 +22,9 @@ class ASH_EXPORT TaskSwitchMetricsRecorder {
   // Enumeration of the different user interfaces that could be the source of
   // a task switch. Note this is not necessarily comprehensive of all sources.
   enum TaskSwitchSource {
+    // Task switches caused by selecting a window from overview mode which is
+    // different from the previously-active window.
+    kOverviewMode,
     // All task switches caused by shelf buttons, not including sub-menus.
     kShelf,
     // All task switches caused by the tab strip.

ash/metrics/task_switch_metrics_recorder_unittest.cc

@@ -107,4 +107,19 @@ TEST_F(TaskSwitchMetricsRecorderTest,
   histogram_tester_->ExpectTotalCount(kHistogramName, 2);
 }
 
+// Verifies that the TaskSwitchMetricsRecorder::kOverviewMode source adds data
+// to the Ash.WindowSelector.TimeBetweenActiveWindowChanges histogram.
+TEST_F(TaskSwitchMetricsRecorderTest,
+       VerifyTaskSwitchesFromOverviewModeAreRecorded) {
+  const std::string kHistogramName =
+      "Ash.WindowSelector.TimeBetweenActiveWindowChanges";
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kOverviewMode);
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kOverviewMode);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 1);
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kOverviewMode);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 2);
+}
+
 }  // namespace ash

ash/metrics/user_metrics_recorder.cc

@@ -584,6 +584,8 @@ void UserMetricsRecorder::RecordUserMetricsAction(UserMetricsAction action) {
     case ash::UMA_WINDOW_OVERVIEW_ACTIVE_WINDOW_CHANGED:
       base::RecordAction(
           base::UserMetricsAction("WindowSelector_ActiveWindowChanged"));
+      task_switch_metrics_recorder_.OnTaskSwitch(
+          TaskSwitchMetricsRecorder::kOverviewMode);
       break;
     case ash::UMA_WINDOW_OVERVIEW_ENTER_KEY:
       base::RecordAction(

tools/metrics/histograms/histograms.xml

@@ -1016,11 +1016,25 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Ash.WindowSelector.TimeBetweenActiveWindowChanges"
+    units="seconds">
+  <owner>bruthig@chromium.org</owner>
+  <owner>tdanderson@chromium.org</owner>
+  <summary>
+    The amount of time between endings of overview mode sessions which were
+    caused by the user selecting a window which was not previously active. Only
+    recorded on the second and later times after startup that the user selected
+    a window which was not previously active.
+  </summary>
+</histogram>
+
 <histogram name="Ash.WindowSelector.TimeBetweenUse" units="milliseconds">
   <owner>flackr@chromium.org</owner>
   <owner>kuscher@google.com</owner>
   <summary>
-    The amount of time between uses of overview mode to switch between windows.
+    The amount of time between uses of overview mode, recorded when overview
+    mode is entered. Only recorded on the second and later times after startup
+    that the user entered overview mode.
   </summary>
 </histogram>