Added UMA statistics for changing the active window via click or touch events.

ui/wm/core/window_activation_pre_target_handler.h

+// 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.
+
+#ifndef UI_WM_CORE_WINDOW_ACTIVATION_PRE_TARGET_HANDLER_H_
+#define UI_WM_CORE_WINDOW_ACTIVATION_PRE_TARGET_HANDLER_H_
+
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "ui/events/event_handler.h"
+#include "ui/wm/wm_export.h"
+
+namespace aura {
+namespace client {
+class ActivationClient;
+}  // namespace client
+}  // namespace aura
+
+namespace wm {
+
+class ActivationClient;
+class WindowActivationPreTargetHandlerObserver;
+
+class WM_EXPORT WindowActivationPreTargetHandler : public ui::EventHandler {

[tdanderson, 2015/05/26 21:13:52]

How about WindowActivationEventHandler?

+ public:
+  explicit WindowActivationPreTargetHandler(
+      aura::client::ActivationClient* activation_client);
+  ~WindowActivationPreTargetHandler() override;
+
+  void AddObserver(WindowActivationPreTargetHandlerObserver* observer);
+  void RemoveObserver(WindowActivationPreTargetHandlerObserver* observer);
+
+  // ui::EventHandler:
+  void OnMouseEvent(ui::MouseEvent* event) override;
+  void OnGestureEvent(ui::GestureEvent* event) override;
+
+ private:
+  aura::client::ActivationClient* activation_client_;
+
+  ObserverList<WindowActivationPreTargetHandlerObserver> observers_;
+
+  void ActivateWindowFromEvent(ui::Event* event);

[tdanderson, 2015/05/26 21:13:52]

nit: members below methods

+
+  DISALLOW_COPY_AND_ASSIGN(WindowActivationPreTargetHandler);
+};
+
+}  // namespace wm
+
+#endif  // UI_WM_CORE_WINDOW_ACTIVATION_PRE_TARGET_HANDLER_H_