Refactor MdFocusRing to make it easier to reuse on other controls.

ui/views/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/ozone/ozone.gni")
 
 config("flags") {
@@ skipping 98 matching lines @@
     "controls/button/radio_button.h",
     "controls/button/toggle_button.cc",
     "controls/button/toggle_button.h",
     "controls/button/vector_icon_button.cc",
     "controls/button/vector_icon_button.h",
     "controls/button/vector_icon_button_delegate.cc",
     "controls/button/vector_icon_button_delegate.h",
     "controls/combobox/combobox.cc",
     "controls/combobox/combobox.h",
     "controls/combobox/combobox_listener.h",
+    "controls/focus_ring.cc",
+    "controls/focus_ring.h",
     "controls/focusable_border.cc",
     "controls/focusable_border.h",
     "controls/focusable_rounded_border_mac.cc",
     "controls/focusable_rounded_border_mac.h",
     "controls/glow_hover_controller.cc",
     "controls/glow_hover_controller.h",
     "controls/image_view.cc",
     "controls/image_view.h",
     "controls/label.cc",
     "controls/label.h",
@@ skipping 879 matching lines @@
       "//ui/base:test_support",
       "//ui/compositor",
       "//ui/events:test_support",
       "//ui/gl:test_support",
       "//ui/resources",
       "//ui/resources:ui_test_pak",
       "//ui/strings",
     ]
   }
 }