[Toolbar] Base toolbar button class with background images for button states

chrome/chrome_browser_ui.gypi

 # Copyright 2012 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.
 
 {
   'targets': [
     {
       'target_name': 'browser_ui',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 2087 matching lines @@
         'browser/ui/views/tabs/tab_controller.h',
         'browser/ui/views/tabs/tab_drag_controller.cc',
         'browser/ui/views/tabs/tab_drag_controller.h',
         'browser/ui/views/tabs/tab_strip.cc',
         'browser/ui/views/tabs/tab_strip.h',
         'browser/ui/views/tabs/tab_strip_controller.h',
         'browser/ui/views/task_manager_view.cc',
         'browser/ui/views/theme_image_mapper.cc',
         'browser/ui/views/theme_image_mapper.h',
         'browser/ui/views/theme_image_mapper_aura_win.cc',
+        'browser/ui/views/toolbar/back_button.cc',
+        'browser/ui/views/toolbar/back_button.h',
         'browser/ui/views/toolbar/browser_action_test_util_views.cc',
         'browser/ui/views/toolbar/browser_action_view.cc',
         'browser/ui/views/toolbar/browser_action_view.h',
         'browser/ui/views/toolbar/browser_actions_container.cc',
         'browser/ui/views/toolbar/browser_actions_container.h',
-        'browser/ui/views/toolbar/button_dropdown.cc',
-        'browser/ui/views/toolbar/button_dropdown.h',
         'browser/ui/views/toolbar/home_button.cc',
         'browser/ui/views/toolbar/home_button.h',
         'browser/ui/views/toolbar/reload_button.cc',
         'browser/ui/views/toolbar/reload_button.h',
+        'browser/ui/views/toolbar/toolbar_button.cc',
+        'browser/ui/views/toolbar/toolbar_button.h',
         'browser/ui/views/toolbar/toolbar_view.cc',
         'browser/ui/views/toolbar/toolbar_view.h',
         'browser/ui/views/toolbar/wrench_menu.cc',
         'browser/ui/views/toolbar/wrench_menu.h',
         'browser/ui/views/toolbar/wrench_menu_observer.h',
         'browser/ui/views/toolbar/wrench_toolbar_button.cc',
         'browser/ui/views/toolbar/wrench_toolbar_button.h',
         'browser/ui/views/top_level_widget_views.cc',
         'browser/ui/views/touch_uma/touch_uma.h',
         'browser/ui/views/translate/translate_bubble_view.cc',
@@ skipping 1216 matching lines @@
             'browser/ui/webui/local_discovery/local_discovery_ui.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui.h',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.cc',
             'browser/ui/webui/local_discovery/local_discovery_ui_handler.h',
           ],
         }],
       ],
     },
   ],
 }