Add another GM to skip in serialize mode.

tools/dm_flags.py

 #
 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 
 #!/usr/bin/env python
 
 usage = '''
@@ skipping 174 matching lines @@
                        'fontmgr_bounds_1_-0.25',
                        'fontmgr_bounds',
                        'fontmgr_match',
                        'fontmgr_iter']
   # skia:5589
   bad_serialize_gms.extend(['bitmapfilters',
                             'bitmapshaders',
                             'bleed',
                             'bleed_alpha_bmp',
                             'bleed_alpha_bmp_shader',
+                            'convex_poly_clip',
                             'extractalpha',
                             'filterbitmap_checkerboard_32_32_g8',
                             'filterbitmap_image_mandrill_64',
                             'shadows',
                             'simpleaaclip_aaclip'])
   for test in bad_serialize_gms:
     blacklist.extend(['serialize-8888', 'gm', '_', test])
 
   if 'Mac' not in bot:
     for test in ['bleed_alpha_image', 'bleed_alpha_image_shader']:
@@ skipping 142 matching lines @@
   if len(sys.argv) == 2 and sys.argv[1] == 'test':
     self_test()
     sys.exit(0)
 
   if len(sys.argv) != 3:
     print usage
     sys.exit(1)
 
   with open(sys.argv[1], 'w') as out:
     json.dump(get_args(sys.argv[2]), out)