IDL: Drop [PerContextEnabled] extended attribute

Source/bindings/scripts/interface_dependency_resolver.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 28 matching lines @@
 import os.path
 from utilities import idl_filename_to_component, is_valid_component_dependency
 
 # The following extended attributes can be applied to a dependency interface,
 # and are then applied to the individual members when merging.
 # Note that this moves the extended attribute from the interface to the member,
 # which changes the semantics and yields different code than the same extended
 # attribute on the main interface.
 DEPENDENCY_EXTENDED_ATTRIBUTES = frozenset([
     'Conditional',
-    'PerContextEnabled',
     'RuntimeEnabled',
     'TypeChecking',
 ])
 
 
 class InterfaceDependencyResolver(object):
     def __init__(self, interfaces_info, reader):
         """Initialize dependency resolver.
 
         Args:
@@ skipping 239 matching lines @@
         for key, value in extras.items():
             if key not in attributes:
                 attributes[key] = value
 
     for attribute in dependency_interface.attributes:
         update_attributes(attribute.extended_attributes, merged_extended_attributes)
     for constant in dependency_interface.constants:
         update_attributes(constant.extended_attributes, merged_extended_attributes)
     for operation in dependency_interface.operations:
         update_attributes(operation.extended_attributes, merged_extended_attributes)