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

ash/metrics/desktop_task_switch_metric_recorder.cc

-// Copyright 2015 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.
-
-#include "ash/metrics/desktop_task_switch_metric_recorder.h"
-
-#include "ash/metrics/user_metrics_recorder.h"
-#include "ash/shell.h"
-#include "ash/wm/window_util.h"
-#include "ui/wm/public/activation_client.h"
-
-namespace ash {
-
-DesktopTaskSwitchMetricRecorder::DesktopTaskSwitchMetricRecorder()
-    : last_active_task_window_(nullptr) {
-  Shell::GetInstance()->activation_client()->AddObserver(this);
-}
-
-DesktopTaskSwitchMetricRecorder::~DesktopTaskSwitchMetricRecorder() {
-  Shell::GetInstance()->activation_client()->RemoveObserver(this);
-}
-
-void DesktopTaskSwitchMetricRecorder::OnWindowActivated(
-    aura::client::ActivationChangeObserver::ActivationReason reason,
-    aura::Window* gained_active,
-    aura::Window* lost_active) {
-  if (gained_active && wm::IsWindowUserPositionable(gained_active)) {
-    if (last_active_task_window_ != gained_active &&
-        reason == aura::client::ActivationChangeObserver::ActivationReason::
-                      INPUT_EVENT) {
-      Shell::GetInstance()->metrics()->RecordUserMetricsAction(
-          UMA_DESKTOP_SWITCH_TASK);
-    }
-    last_active_task_window_ = gained_active;
-  }
-}
-
-}  // namespace ash