Remove obsolete mac_gpu

tools/roll_deps.py

 #!/usr/bin/python2
 
 # Copyright 2014 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Skia's Chromium DEPS roll script.
 
 This script:
@@ skipping 34 matching lines @@
   'linux',
   'linux_asan',
   'linux_chromeos',
   'linux_chromeos_asan',
   'linux_chromium_gn_dbg',
   'linux_gpu',
   'linux_layout',
   'linux_layout_rel',
   'mac',
   'mac_asan',
-  'mac_gpu',
   'mac_layout',
   'mac_layout_rel',
   'win',
   'win_gpu',
   'win_layout',
   'win_layout_rel',
 ]
 
 REGEXP_SKIA_REVISION = (
     r'^  "skia_revision": "(?P<revision>[0-9a-fA-F]{2,40})",$')
@@ skipping 223 matching lines @@
 
   if deps_issue and whitespace_issue:
     print 'DEPS roll:\n    %s\n' % deps_issue
     print 'Whitespace change:\n    %s\n' % whitespace_issue
   else:
     print >> sys.stderr, 'No issues created.'
 
 
 if __name__ == '__main__':
   main(sys.argv[1:])