Add config options to run different GPU APIs to dm and nanobench

gyp/flags.gyp

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # GYP file to build flag parser
 #
 {
   'targets': [
     {
       'target_name': 'flags',
@@ skipping 14 matching lines @@
           '../tools/flags',
         ],
       }
     },
     {
       'target_name': 'flags_common',
       'type': 'static_library',
       'sources': [
         '../tools/flags/SkCommonFlags.cpp',
         '../tools/flags/SkCommonFlags.h',
+        '../tools/flags/SkCommonFlagsConfig.cpp',
+        '../tools/flags/SkCommonFlagsConfig.h',
       ],
       'dependencies': [
         'skia_lib.gyp:skia_lib',
         'flags.gyp:flags',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../tools/flags',
         ],
       }
     },
   ],
 }