Add [CachedAccessor] attribute to cache (almost) constant accessors (window.document).

third_party/WebKit/Source/bindings/scripts/v8_attributes.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 86 matching lines @@
     if (base_idl_type == 'EventHandler' and
             interface.name in ['Window', 'WorkerGlobalScope'] and
             attribute.name == 'onerror'):
         includes.add('bindings/core/v8/V8ErrorHandler.h')
 
     cached_attribute_validation_method = extended_attributes.get('CachedAttribute')
     keep_alive_for_gc = is_keep_alive_for_gc(interface, attribute)
     if cached_attribute_validation_method or keep_alive_for_gc:
         includes.add('bindings/core/v8/V8HiddenValue.h')
 
+    # [CachedAccessor]
+    is_cached_accessor = 'CachedAccessor' in extended_attributes
+    if is_cached_accessor:
+        includes.add('bindings/core/v8/V8PrivateProperty.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]
         'argument_cpp_type': idl_type.cpp_type_args(used_as_rvalue_type=True),
         'cached_attribute_validation_method': cached_attribute_validation_method,
         'constructor_type': constructor_type,
         'cpp_name': cpp_name(attribute),
         'cpp_type': idl_type.cpp_type,
         'cpp_type_initializer': idl_type.cpp_type_initializer,
         'deprecate_as': v8_utilities.deprecate_as(attribute),  # [DeprecateAs]
         'enum_type': idl_type.enum_type,
         'enum_values': idl_type.enum_values,
         'exposed_test': v8_utilities.exposed(attribute, interface),  # [Exposed]
         'has_custom_getter': has_custom_getter(attribute),
         'has_custom_setter': has_custom_setter(attribute),
         'has_setter': has_setter(interface, attribute),
         'idl_type': str(idl_type),  # need trailing [] on array for Dictionary::ConversionContext::setConversionType
+        'is_cached_accessor': is_cached_accessor,
         '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_ce_reactions': is_ce_reactions,
         'is_check_security_for_receiver': is_check_security_for_receiver,
         'is_check_security_for_return_value': is_check_security_for_return_value,
         'is_custom_element_callbacks': is_custom_element_callbacks,
         # TODO(yukishiino): Make all DOM attributes accessor-type properties.
-        'is_data_type_property': is_data_type_property(interface, attribute),
+        'is_data_type_property': not ('CachedAccessor' in extended_attributes) and is_data_type_property(interface, attribute),
         'is_getter_raises_exception':  # [RaisesException]
             'RaisesException' in extended_attributes and
             extended_attributes['RaisesException'] in (None, 'Getter'),
         'is_implemented_in_private_script': is_implemented_in_private_script,
         'is_keep_alive_for_gc': keep_alive_for_gc,
         'is_lenient_this': 'LenientThis' in extended_attributes,
         'is_nullable': idl_type.is_nullable,
         'is_explicit_nullable': idl_type.is_explicit_nullable,
         'is_partial_interface_member':
             'PartialInterfaceImplementedAs' in extended_attributes,
@@ skipping 19 matching lines @@
             extended_attributes, 'v8Value', 'cppValue', bailout_return_value='false', isolate='scriptState->isolate()'),
         'property_attributes': property_attributes(interface, attribute),
         'reflect_empty': extended_attributes.get('ReflectEmpty'),
         'reflect_invalid': extended_attributes.get('ReflectInvalid', ''),
         'reflect_missing': extended_attributes.get('ReflectMissing'),
         'reflect_only': extended_attribute_value_as_list(attribute, 'ReflectOnly'),
         'runtime_enabled_function': v8_utilities.runtime_enabled_function_name(attribute),  # [RuntimeEnabled]
         'runtime_feature_name': v8_utilities.runtime_feature_name(attribute),  # [RuntimeEnabled]
         'secure_context_test': v8_utilities.secure_context(attribute, interface),  # [SecureContext]
         'should_be_exposed_to_script': not (is_implemented_in_private_script and is_only_exposed_to_private_script),
+        'cached_accessor_name': '%s%sCachedAccessor' % (interface.name, attribute.name.capitalize()),
         'world_suffixes': (
             ['', 'ForMainWorld']
             if 'PerWorldBindings' in extended_attributes
             else ['']),  # [PerWorldBindings]
     }
 
     if is_constructor_attribute(attribute):
         update_constructor_attribute_context(interface, attribute, context)
     if not has_custom_getter(attribute):
         getter_context(interface, attribute, context)
@@ skipping 385 matching lines @@
     lambda self: strip_suffix(self.base_type, 'Constructor'))
 
 
 def is_constructor_attribute(attribute):
     # FIXME: replace this with [ConstructorAttribute] extended attribute
     return attribute.idl_type.name.endswith('Constructor')
 
 
 def update_constructor_attribute_context(interface, attribute, context):
     context['needs_constructor_getter_callback'] = context['measure_as'] or context['deprecate_as']