Generate simple code for "trivial" conversions

Source/bindings/scripts/v8_methods.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 55 matching lines @@
         # String and enumeration arguments converted using one of the
         # TOSTRING_* macros except for _PROMISE variants in
         # Source/bindings/core/v8/V8BindingMacros.h don't use a v8::TryCatch.
         ((base_type == 'DOMString' or idl_type.is_enum) and
          not argument.is_variadic and
          not return_promise) or
         # Conversion that take an ExceptionState& argument throw all their
         # exceptions via it, and doesn't need/use a TryCatch, except if the
         # argument has [Clamp], in which case it uses a separate code path in
         # Source/bindings/templates/methods.cpp, which *does* use a TryCatch.
-        idl_type.v8_conversion_needs_exception_state)
+        idl_type.v8_conversion_needs_exception_state or
+        # A trivial conversion cannot throw exceptions at all, so doesn't need a
+        # TryCatch to catch them.
+        idl_type.v8_conversion_is_trivial)
 
 
 def use_local_result(method):
     extended_attributes = method.extended_attributes
     idl_type = method.idl_type
     return (has_extended_attribute_value(method, 'CallWith', 'ScriptState') or
             'ImplementedInPrivateScript' in extended_attributes or
             'RaisesException' in extended_attributes or
             idl_type.is_union_type or
             idl_type.is_explicit_nullable)
@@ skipping 371 matching lines @@
     if argument.idl_type.is_dictionary:
         # We always create impl objects for IDL dictionaries.
         return '%s::create()' % argument.idl_type.base_type
     if not argument.default_value:
         return None
     return argument.idl_type.literal_cpp_value(argument.default_value)
 
 IdlTypeBase.union_arguments = None
 IdlUnionType.union_arguments = property(union_arguments)
 IdlArgument.default_cpp_value = property(argument_default_cpp_value)