[bindings] Implement an ExperimentEnabled IDL extended attribute.

third_party/WebKit/Source/bindings/scripts/code_generator_v8.py

 # 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
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 405 matching lines @@
 # [Conditional]
 def conditional_if_endif(code, conditional_string):
     # Jinja2 filter to generate if/endif directive blocks
     if not conditional_string:
         return code
     return ('#if %s\n' % conditional_string +
             code +
             '#endif // %s\n' % conditional_string)
 
 
+def maybe_add_conditional(code, test, conditional):
+    if not test:
+        return code
+    return generate_indented_conditional(code, conditional)
+
 # [Exposed]
 def exposed_if(code, exposed_test):
-    if not exposed_test:
-        return code
-    return generate_indented_conditional(code, 'executionContext && (%s)' % exposed_test)
+    return maybe_add_conditional(code, exposed_test, 'executionContext && (%s)' % exposed_test)
 
 
 # [RuntimeEnabled]
 def runtime_enabled_if(code, runtime_enabled_function_name):
-    if not runtime_enabled_function_name:
-        return code
-    return generate_indented_conditional(code, '%s()' % runtime_enabled_function_name)
+    return maybe_add_conditional(code, runtime_enabled_function_name, '%s()' % runtime_enabled_function_name)
 
 
 ################################################################################
 
 def main(argv):
     # If file itself executed, cache templates
     try:
         cache_dir = argv[1]
         dummy_filename = argv[2]
     except IndexError as err:
@@ skipping 10 matching lines @@
 
     # Create a dummy file as output for the build system,
     # since filenames of individual cache files are unpredictable and opaque
     # (they are hashes of the template path, which varies based on environment)
     with open(dummy_filename, 'w') as dummy_file:
         pass  # |open| creates or touches the file
 
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))