nullptr -> "sans-serif" fixes bold in gm/colorwheel

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 146 matching lines @@
     blacklist.extend('_ image gen_platf 24bpp-pixeldata-cropped.bmp'.split(' '))
 
   # skia:4095
   for test in ['not_native32_bitmap_config',
                'bleed_image',
                'bleed_alpha_image',
                'bleed_alpha_image_shader',
                'c_gms',
                'colortype',
                'colortype_xfermodes',
-               'colorwheelnative',
                'drawfilter',
                'fontmgr_bounds_0.75_0',
                'fontmgr_bounds_1_-0.25',
                'fontmgr_bounds',
                'fontmgr_match',
                'fontmgr_iter',
                'verylargebitmap',              # Windows only.
                'verylarge_picture_image']:     # Windows only.
     blacklist.extend(['serialize-8888', 'gm', '_', test])
   # skia:4769
@@ skipping 115 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)