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

ui/wm/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 component("wm") {
   sources = [
     "core/accelerator_delegate.h",
@@ skipping 41 matching lines @@
     "core/shadow_types.h",
     "core/transient_window_controller.cc",
     "core/transient_window_controller.h",
     "core/transient_window_manager.cc",
     "core/transient_window_manager.h",
     "core/transient_window_observer.h",
     "core/transient_window_stacking_client.cc",
     "core/transient_window_stacking_client.h",
     "core/visibility_controller.cc",
     "core/visibility_controller.h",
+    "core/window_activation_pre_target_handler.cc",
+    "core/window_activation_pre_target_handler.h",
+    "core/window_activation_pre_target_handler_observer.cc",
+    "core/window_activation_pre_target_handler_observer.h",
     "core/window_animations.cc",
     "core/window_animations.h",
     "core/window_modality_controller.cc",
     "core/window_modality_controller.h",
     "core/window_util.cc",
     "core/window_util.h",
     "core/wm_core_switches.cc",
     "core/wm_core_switches.h",
     "core/wm_state.cc",
     "core/wm_state.h",
@@ skipping 71 matching lines @@
     "//ui/base:test_support",
     "//ui/base/ime",
     "//ui/compositor:test_support",
     "//ui/events:test_support",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 }