Revert r333104: "Added UMA statistics for changing the active window via click or touch events."

ash/metrics/task_switch_metrics_recorder.cc

Index: ash/metrics/task_switch_metrics_recorder.cc
diff --git a/ash/metrics/task_switch_metrics_recorder.cc b/ash/metrics/task_switch_metrics_recorder.cc
index 11ba222f9a724fb758d2d315e9a8d19dbe33c1b8..b8b57fe4753606428c68f2be1236c100070d10c9 100644
--- a/ash/metrics/task_switch_metrics_recorder.cc
+++ b/ash/metrics/task_switch_metrics_recorder.cc
@@ -10,9 +10,6 @@ namespace ash {
 
 namespace {
 
-const char kDesktopHistogramName[] =
-    "Ash.Desktop.TimeBetweenNavigateToTaskSwitches";
-
 const char kShelfHistogramName[] =
     "Ash.Shelf.TimeBetweenNavigateToTaskSwitches";
 
@@ -33,8 +30,6 @@ const char* GetHistogramName(
   switch (task_switch_source) {
     case TaskSwitchMetricsRecorder::kAppList:
       return kAppListHistogramName;
-    case TaskSwitchMetricsRecorder::kDesktop:
-      return kDesktopHistogramName;
     case TaskSwitchMetricsRecorder::kOverviewMode:
       return kOverviewModeHistogramName;
     case TaskSwitchMetricsRecorder::kShelf: