[bindings] Implement an ExperimentEnabled IDL extended attribute.

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

Index: third_party/WebKit/Source/bindings/templates/attributes.cpp
diff --git a/third_party/WebKit/Source/bindings/templates/attributes.cpp b/third_party/WebKit/Source/bindings/templates/attributes.cpp
index b7fdd10e8bdf20951dcd8069be2520ed2801dbea..6991c14d989222411137c8cf30a37247603c43fa 100644
--- a/third_party/WebKit/Source/bindings/templates/attributes.cpp
+++ b/third_party/WebKit/Source/bindings/templates/attributes.cpp
@@ -1,5 +1,5 @@
 {% from 'conversions.cpp' import declare_enum_validation_variable, v8_value_to_local_cpp_value %}
-
+{% from 'api_experiment.cpp' import check_api_experiment %}
 
 {##############################################################################}
 {% macro attribute_getter(attribute, world_suffix) %}
@@ -11,6 +11,9 @@ const v8::PropertyCallbackInfo<v8::Value>& info
 const v8::FunctionCallbackInfo<v8::Value>& info
 {%- endif %})
 {
+    {% filter trim %}

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

Why is trim needed?

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

I was having spacing issues because the macro was returning nothing sometimes,
causing the "| indent| to leave 4 whitespaces, which caused a presubmit error.

By adding an if-statement guard around the macro, I've avoided the problem and
fixed the whitespace issues that the trim caused.

+    {{check_api_experiment(attribute) | indent}}
+    {% endfilter %}
     {% if attribute.is_reflect and not attribute.is_url
           and attribute.idl_type == 'DOMString' and is_node
           and not attribute.is_implemented_in_private_script %}
@@ -178,6 +181,9 @@ const v8::FunctionCallbackInfo<v8::Value>& info
     {% if attribute.measure_as %}
     UseCounter::countIfNotPrivateScript(info.GetIsolate(), callingExecutionContext(info.GetIsolate()), UseCounter::{{attribute.measure_as('AttributeGetter')}});
     {% endif %}
+    {% filter trim %}
+    {{check_api_experiment(attribute) | indent}}
+    {% endfilter %}
     {% if world_suffix in attribute.activity_logging_world_list_for_getter %}
     ScriptState* scriptState = ScriptState::from(info.GetIsolate()->GetCurrentContext());
     V8PerContextData* contextData = scriptState->perContextData();
@@ -211,6 +217,9 @@ static void {{attribute.name}}ConstructorGetterCallback{{world_suffix}}(v8::Loca
     {% if attribute.measure_as %}
     UseCounter::countIfNotPrivateScript(info.GetIsolate(), callingExecutionContext(info.GetIsolate()), UseCounter::{{attribute.measure_as('ConstructorGetter')}});
     {% endif %}
+    {% filter trim %}
+    {{check_api_experiment(attribute) | indent}}
+    {% endfilter %}
     v8ConstructorAttributeGetter(property, info);
     TRACE_EVENT_SET_SAMPLING_STATE("v8", "V8Execution");
 }
@@ -418,6 +427,10 @@ bool {{v8_class}}::PrivateScript::{{attribute.name}}AttributeGetter(LocalFrame*
     if (holder.IsEmpty())
         return false;
 
+    {% filter trim %}
+    {{check_api_experiment(attribute) | indent}}
+    {% endfilter %}
+
     ExceptionState exceptionState(ExceptionState::GetterContext, "{{attribute.name}}", "{{cpp_class}}", scriptState->context()->Global(), scriptState->isolate());
     v8::Local<v8::Value> v8Value = PrivateScriptRunner::runDOMAttributeGetter(scriptState, scriptStateInUserScript, "{{cpp_class}}", "{{attribute.name}}", holder);
     if (v8Value.IsEmpty())