Remove the no-longer used TabButtonGtk class.

chrome/chrome.gyp

 # Copyright (c) 2009 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     '../build/common.gypi',
@@ skipping 864 matching lines @@
         'browser/gtk/slide_animator_gtk.cc',
         'browser/gtk/slide_animator_gtk.h',
         'browser/gtk/standard_menus.cc',
         'browser/gtk/standard_menus.h',
         'browser/gtk/status_bubble_gtk.cc',
         'browser/gtk/status_bubble_gtk.h',
         'browser/gtk/tab_contents_container_gtk.cc',
         'browser/gtk/tab_contents_container_gtk.h',
         'browser/gtk/tabs/dragged_tab_controller_gtk.cc',
         'browser/gtk/tabs/dragged_tab_controller_gtk.h',
-        'browser/gtk/tabs/tab_button_gtk.cc',
-        'browser/gtk/tabs/tab_button_gtk.h',
         'browser/gtk/tabs/tab_gtk.cc',
         'browser/gtk/tabs/tab_gtk.h',
         'browser/gtk/tabs/tab_renderer_gtk.cc',
         'browser/gtk/tabs/tab_renderer_gtk.h',
         'browser/gtk/tabs/tab_strip_gtk.cc',
         'browser/gtk/tabs/tab_strip_gtk.h',
         'browser/gtk/toolbar_star_toggle_gtk.cc',
         'browser/gtk/toolbar_star_toggle_gtk.h',
         'browser/hang_monitor/hung_plugin_action.cc',
         'browser/hang_monitor/hung_plugin_action.h',
@@ skipping 2346 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],
   ],  # 'conditions'
 }