ash: Start/stop observing KeyboardController via ShellObserver

ash/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/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 # Historical note: Ash shipped on Windows for a couple years to support
@@ skipping 90 matching lines @@
     "common/frame/header_painter.h",
     "common/frame/header_painter_util.cc",
     "common/frame/header_painter_util.h",
     "common/frame/header_view.cc",
     "common/frame/header_view.h",
     "common/gpu_support.h",
     "common/gpu_support_stub.cc",
     "common/gpu_support_stub.h",
     "common/key_event_watcher.cc",
     "common/key_event_watcher.h",
+    "common/keyboard/keyboard_observer_register.cc",
+    "common/keyboard/keyboard_observer_register.h",
     "common/keyboard/keyboard_ui.cc",
     "common/keyboard/keyboard_ui.h",
     "common/keyboard/keyboard_ui_observer.h",
     "common/login_status.h",
     "common/material_design/material_design_controller.cc",
     "common/material_design/material_design_controller.h",
     "common/media_controller.cc",
     "common/media_controller.h",
     "common/metrics/gesture_action_type.h",
     "common/metrics/pointer_metrics_recorder.cc",
@@ skipping 1383 matching lines @@
     "//content/public/app:both",
     "//device/bluetooth",
   ]
 
   data_deps = [
     "//ash/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_with_content_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }