API functions returning Promises should not throw exceptions.

Source/bindings/scripts/v8_interface.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 # coding=utf-8
 #
 # 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
@@ skipping 832 matching lines @@
     l.sort(key=key)
     return ((k, list(g)) for k, g in itertools.groupby(l, key))
 
 
 ################################################################################
 # Constructors
 ################################################################################
 
 # [Constructor]
 def constructor_context(interface, constructor):
-    arguments_need_try_catch = any(v8_methods.argument_needs_try_catch(argument)
+    arguments_need_try_catch = any(v8_methods.argument_needs_try_catch(argument, async=False)
                                    for argument in constructor.arguments)
 
     # [RaisesException=Constructor]
     is_constructor_raises_exception = \
         interface.extended_attributes.get('RaisesException') == 'Constructor'
 
     return {
         'arguments': [v8_methods.argument_context(interface, constructor, argument, index)
                       for index, argument in enumerate(constructor.arguments)],
         'arguments_need_try_catch': arguments_need_try_catch,
@@ skipping 238 matching lines @@
         deleter = next(
             method
             for method in interface.operations
             if ('deleter' in method.specials and
                 len(method.arguments) == 1 and
                 str(method.arguments[0].idl_type) == 'DOMString'))
     except StopIteration:
         return None
 
     return property_deleter(deleter)