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

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 f27015b2e7e865dd0506b293046eabdb2841326a..4375ff9e3b8e7a791d2a133fc91ab5954f45d7f8 100644
--- a/third_party/WebKit/Source/bindings/scripts/v8_attributes.py
+++ b/third_party/WebKit/Source/bindings/scripts/v8_attributes.py
@@ -119,12 +119,12 @@ def attribute_context(interface, attribute):
         'enum_type': idl_type.enum_type,
         'enum_values': idl_type.enum_values,
         'exposed_test': v8_utilities.exposed(attribute, interface),  # [Exposed]
-        'has_fast_accessor': 'FastAccessor' in extended_attributes,
         'has_custom_getter': has_custom_getter(attribute),
         'has_custom_setter': has_custom_setter(attribute),
         'has_fast_accessor': 'FastAccessor' in extended_attributes,
         'has_setter': has_setter(interface, attribute),
         'idl_type': str(idl_type),  # need trailing [] on array for Dictionary::ConversionContext::setConversionType
+        'is_cached_accessor': 'CachedAccessor' in extended_attributes,
         '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,
@@ -132,7 +132,7 @@ def attribute_context(interface, attribute):
         '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'),
@@ -172,6 +172,7 @@ def attribute_context(interface, attribute):
         '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),
+        'cache_property_name': '%s%s' % (interface.name, attribute.name.capitalize()),

[haraken, 2016/09/20 14:15:03]

cached_accessor_name

         'world_suffixes': (
             ['', 'ForMainWorld']
             if 'PerWorldBindings' in extended_attributes