Remove obsolete files from 'sources'. This causes needless work on incrementa...

app/app_base.gypi

 # Copyright (c) 2011 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.
 
 {
   'target_defaults': {
     'variables': {
       'app_base_target': 0,
     },
     'target_conditions': [
@@ skipping 188 matching lines @@
         'gfx/gl/gl_bindings.h',
         'gfx/gl/gl_context.cc',
         'gfx/gl/gl_context.h',
         'gfx/gl/gl_context_linux.cc',
         'gfx/gl/gl_context_mac.cc',
         'gfx/gl/gl_context_osmesa.cc',
         'gfx/gl/gl_context_osmesa.h',
         'gfx/gl/gl_context_stub.cc',
         'gfx/gl/gl_context_stub.h',
         'gfx/gl/gl_context_win.cc',
-        'gfx/gl/gl_headers.h',
         'gfx/gl/gl_implementation.cc',
         'gfx/gl/gl_implementation.h',
         'gfx/gl/gl_implementation_linux.cc',
         'gfx/gl/gl_implementation_mac.cc',
         'gfx/gl/gl_implementation_win.cc',
         'gfx/gl/gl_interface.h',
         'gfx/gl/gl_interface.cc',
         'mac/nsimage_cache.h',
         'mac/nsimage_cache.mm',
         'mac/scoped_nsdisable_screen_updates.h',
@@ skipping 234 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }