Add a public API to enable/disable blink runtime features by name

Source/core/scripts/make_runtime_features.py

 #!/usr/bin/env python
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 26 matching lines @@
 
 class RuntimeFeatureWriter(in_generator.Writer):
     class_name = 'RuntimeEnabledFeatures'
 
     # FIXME: valid_values and defaults should probably roll into one object.
     valid_values = {
         'status': ['stable', 'experimental', 'test'],
     }
     defaults = {
         'condition' : None,
+        'command_line_flag': False,
         'depends_on' : [],
         'custom': False,
         'status': None,
     }
 
     def __init__(self, in_file_path, enabled_conditions):
         super(RuntimeFeatureWriter, self).__init__(in_file_path, enabled_conditions)
         self._outputs = {(self.class_name + ".h"): self.generate_header,
                          (self.class_name + ".cpp"): self.generate_implementation,
                         }
@@ skipping 33 matching lines @@
     @template_expander.use_jinja(class_name + ".cpp.tmpl")
     def generate_implementation(self):
         return {
             'features': self._features,
             'feature_sets': self._feature_sets(),
         }
 
 
 if __name__ == "__main__":
     in_generator.Maker(RuntimeFeatureWriter).main(sys.argv)