[bindings] Implement an ExperimentEnabled IDL extended attribute.

third_party/WebKit/Source/bindings/scripts/v8_attributes.py

Index: third_party/WebKit/Source/bindings/scripts/v8_attributes.py
diff --git a/third_party/WebKit/Source/bindings/scripts/v8_attributes.py b/third_party/WebKit/Source/bindings/scripts/v8_attributes.py
index 96b8964d46a8f781f270a528c79b2ac3a8f90be0..277bbbc18bf2793c02e6d23e64f0aad5a1fbdfba 100644
--- a/third_party/WebKit/Source/bindings/scripts/v8_attributes.py
+++ b/third_party/WebKit/Source/bindings/scripts/v8_attributes.py
@@ -98,11 +98,18 @@ def attribute_context(interface, attribute):
     if cached_attribute_validation_method or keep_alive_for_gc:
         includes.add('bindings/core/v8/V8HiddenValue.h')
 
+    if 'APIExperimentEnabled' in extended_attributes:
+        includes.add('core/experiments/ExperimentalFeatures.h')
+        includes.add('core/inspector/ConsoleMessage.h')
+
     context = {
         'access_control_list': access_control_list(interface, attribute),
         'activity_logging_world_list_for_getter': v8_utilities.activity_logging_world_list(attribute, 'Getter'),  # [ActivityLogging]
         'activity_logging_world_list_for_setter': v8_utilities.activity_logging_world_list(attribute, 'Setter'),  # [ActivityLogging]
         'activity_logging_world_check': v8_utilities.activity_logging_world_check(attribute),  # [ActivityLogging]
+        'api_experiment_enabled': v8_utilities.api_experiment_enabled_function(attribute),  # [APIExperimentEnabled]
+        'api_experiment_enabled_per_interface': v8_utilities.api_experiment_enabled_function(interface),  # [APIExperimentEnabled]
+        'api_experiment_name': extended_attributes.get('APIExperimentEnabled'),  # [APIExperimentEnabled]
         'argument_cpp_type': idl_type.cpp_type_args(used_as_rvalue_type=True),
         'cached_attribute_validation_method': cached_attribute_validation_method,
         'conditional_string': conditional_string,
@@ -118,6 +125,7 @@ def attribute_context(interface, attribute):
         'has_custom_setter': has_custom_setter(attribute),
         'has_setter': has_setter(attribute),
         'idl_type': str(idl_type),  # need trailing [] on array for Dictionary::ConversionContext::setConversionType
+        'is_api_experiment_enabled': v8_utilities.api_experiment_enabled_function(attribute) or v8_utilities.api_experiment_enabled_function(interface),  # [APIExperimentEnabled]
         'is_call_with_execution_context': has_extended_attribute_value(attribute, 'CallWith', 'ExecutionContext'),
         'is_call_with_script_state': has_extended_attribute_value(attribute, 'CallWith', 'ScriptState'),
         'is_check_security_for_receiver': is_check_security_for_receiver,
@@ -509,7 +517,7 @@ def is_constructor_attribute(attribute):
 
 
 def update_constructor_attribute_context(interface, attribute, context):
-    context['needs_constructor_getter_callback'] = context['measure_as'] or context['deprecate_as']
+    context['needs_constructor_getter_callback'] = context['measure_as'] or context['deprecate_as'] or context['api_experiment_name']
     # When the attribute name is the same as the interface name, do not generate
     # callback functions for each attribute and use
     # {{cpp_class}}ConstructorAttributeSetterCallback.  Otherwise, generate