[bindings] Implement an ExperimentEnabled IDL extended attribute.

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

Index: third_party/WebKit/Source/bindings/scripts/code_generator_v8.py
diff --git a/third_party/WebKit/Source/bindings/scripts/code_generator_v8.py b/third_party/WebKit/Source/bindings/scripts/code_generator_v8.py
index 110e8e86368557bf0d9baeb3df52de50ff09503d..a08c3acfde1e98b45a7f669ae60c62ebe552442f 100644
--- a/third_party/WebKit/Source/bindings/scripts/code_generator_v8.py
+++ b/third_party/WebKit/Source/bindings/scripts/code_generator_v8.py
@@ -423,18 +423,19 @@ def conditional_if_endif(code, conditional_string):
             '#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)
 
 
 ################################################################################