Record time between selecting items from the Ash app list

Add the histogram Ash.AppList.TimeBetweenTaskSwitches
to record the time between selecting items from
the app list (launcher) in Ash.

BUG=478933
TEST=TaskSwitchMetricsRecorderTest.VerifyTaskSwitchesFromAppListAreRecorded

Review URL: https://codereview.chromium.org/1145453003

Cr-Commit-Position: refs/heads/master@{#330276}

ash/metrics/task_switch_metrics_recorder.cc

@@ -19,6 +19,8 @@ const char kTabStripHistogramName[] =
 const char kAcceleratorWindowCycleHistogramName[] =
     "Ash.WindowCycleController.TimeBetweenTaskSwitches";
 
+const char kAppListHistogramName[] = "Ash.AppList.TimeBetweenTaskSwitches";
+
 const char kOverviewModeHistogramName[] =
     "Ash.WindowSelector.TimeBetweenActiveWindowChanges";
 
@@ -26,6 +28,8 @@ const char kOverviewModeHistogramName[] =
 const char* GetHistogramName(
     TaskSwitchMetricsRecorder::TaskSwitchSource task_switch_source) {
   switch (task_switch_source) {
+    case TaskSwitchMetricsRecorder::kAppList:
+      return kAppListHistogramName;
     case TaskSwitchMetricsRecorder::kOverviewMode:
       return kOverviewModeHistogramName;
     case TaskSwitchMetricsRecorder::kShelf:

ash/metrics/task_switch_metrics_recorder.h

@@ -22,6 +22,8 @@ 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 from selecting items in the app list.
+    kAppList,
     // Task switches caused by selecting a window from overview mode which is
     // different from the previously-active window.
     kOverviewMode,

ash/metrics/task_switch_metrics_recorder_unittest.cc

@@ -122,4 +122,18 @@ TEST_F(TaskSwitchMetricsRecorderTest,
   histogram_tester_->ExpectTotalCount(kHistogramName, 2);
 }
 
+// Verifies that the TaskSwitchMetricsRecorder::kAppList source adds data to the
+// Ash.AppList.TimeBetweenTaskSwitches histogram.
+TEST_F(TaskSwitchMetricsRecorderTest,
+       VerifyTaskSwitchesFromApplistAreRecorded) {
+  const std::string kHistogramName = "Ash.AppList.TimeBetweenTaskSwitches";
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kAppList);
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kAppList);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 1);
+
+  OnTaskSwitch(TaskSwitchMetricsRecorder::kAppList);
+  histogram_tester_->ExpectTotalCount(kHistogramName, 2);
+}
+
 }  // namespace ash

chrome/browser/ui/ash/app_list/app_list_controller_ash.cc

@@ -4,6 +4,7 @@
 
 #include "chrome/browser/ui/ash/app_list/app_list_controller_ash.h"
 
+#include "ash/metrics/task_switch_metrics_recorder.h"
 #include "ash/shell.h"
 #include "chrome/browser/ui/ash/launcher/chrome_launcher_controller.h"
 #include "chrome/browser/ui/browser_navigator.h"
@@ -101,6 +102,11 @@ void AppListControllerDelegateAsh::ActivateApp(
     const extensions::Extension* extension,
     AppListSource source,
     int event_flags) {
+  ash::Shell::GetInstance()
+      ->metrics()
+      ->task_switch_metrics_recorder()
+      .OnTaskSwitch(ash::TaskSwitchMetricsRecorder::kAppList);
+
   // Platform apps treat activations as a launch. The app can decide whether to
   // show a new window or focus an existing window as it sees fit.
   if (extension->is_platform_app()) {

tools/metrics/histograms/histograms.xml

@@ -605,6 +605,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Ash.AppList.TimeBetweenTaskSwitches" units="seconds">
+  <owner>bruthig@chromium.org</owner>
+  <owner>tdanderson@chromium.org</owner>
+  <summary>
+    The amount of time between selecting an item from the Ash app list. Not
+    recorded on the first time an item is selected from the app list after
+    startup.
+  </summary>
+</histogram>
+
 <histogram name="Ash.Dock.Action" enum="DockedAction">
   <owner>kuscher@google.com</owner>
   <owner>varkha@chromium.org</owner>