[bindings] Implement an ExperimentEnabled IDL extended attribute.

third_party/WebKit/Source/bindings/templates/api_experiment.cpp

+{% macro check_api_experiment_internal(errorName, experiment_name) %}

[haraken, 2015/12/30 00:25:32]

Could you move this macro to conversions.cpp (and avoid introducing this file)?

Actually conversions.cpp should be renamed to utilities.cpp... (You don't need
to rename it in this CL.)

[Daniel Nishi, 2015/12/30 22:05:50]

Done.

+{% if experiment_name %}
+String {{errorName}};
+if (!{{experiment_name}}(currentExecutionContext(info.GetIsolate()), {{errorName}})) {
+     v8SetReturnValue(info, v8::Undefined(info.GetIsolate()));
+     Document& document = *toDocument(currentExecutionContext(info.GetIsolate()));

[haraken, 2015/12/30 00:25:32]

Avoid calling currentExecutionContext twice.

[Daniel Nishi, 2015/12/30 22:05:50]

Done.

+     document.addConsoleMessage(ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, {{errorName}}));
+     return;
+}
+{% endif %}
+{% endmacro %}
+{% macro check_api_experiment(member) %}
+{{check_api_experiment_internal("errorMessage", member.api_experiment_inherited_enabled)}}
+{{check_api_experiment_internal("memberErrorMessage", member.api_experiment_enabled)}}
+{% endmacro %}