Create fewer local v8::TryCatch objects in generated bindings code

Source/bindings/scripts/v8_types.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 413 matching lines @@
         expression_format = '(to{ref_ptr_type}NativeArray<{array_or_sequence_type}, V8{array_or_sequence_type}>({v8_value}, {index}, info.GetIsolate()))'
         add_includes_for_type(array_or_sequence_type)
     else:
         ref_ptr_type = None
         this_cpp_type = array_or_sequence_type.cpp_type
         expression_format = 'toNativeArray<{cpp_type}>({v8_value}, {index}, info.GetIsolate())'
     expression = expression_format.format(array_or_sequence_type=array_or_sequence_type.name, cpp_type=this_cpp_type, index=index, ref_ptr_type=ref_ptr_type, v8_value=v8_value)
     return expression
 
 
-def v8_value_to_local_cpp_value(idl_type, extended_attributes, v8_value, variable_name, index=None):
+def v8_value_to_local_cpp_value(idl_type, extended_attributes, v8_value, variable_name, index=None, declare_variable=True):
     """Returns an expression that converts a V8 value to a C++ value and stores it as a local value."""
     this_cpp_type = idl_type.cpp_type_args(extended_attributes=extended_attributes, used_as_argument=True)
 
     idl_type = idl_type.preprocessed_type
     cpp_value = v8_value_to_cpp_value(idl_type, extended_attributes, v8_value, index)
-    args = [this_cpp_type, variable_name, cpp_value]
+    args = [variable_name, cpp_value]
     if idl_type.base_type == 'DOMString' and not idl_type.array_or_sequence_type:
         macro = 'TOSTRING_VOID'
     elif idl_type.is_integer_type:
         macro = 'TONATIVE_VOID_EXCEPTIONSTATE'
         args.append('exceptionState')
     else:
         macro = 'TONATIVE_VOID'
 
+    if not declare_variable:

[Nils Barth (inactive), 2014/05/07 03:02:19]

I prefer to avoid 'not' in if...else, so:
if declare_variable:
     args.insert
else:
    macro += ...

+        # Use a macro that assumes a previously declared local variable.
+        macro += "_NO_DECL"

[Nils Barth (inactive), 2014/05/07 03:02:19]

...and single quotes.

+    else:
+        args.insert(0, this_cpp_type)
+
     return '%s(%s)' % (macro, ', '.join(args))
 
 IdlType.v8_value_to_local_cpp_value = v8_value_to_local_cpp_value
 IdlUnionType.v8_value_to_local_cpp_value = v8_value_to_local_cpp_value
 
 
 ################################################################################
 # C++ -> V8
 ################################################################################
 
@@ skipping 182 matching lines @@
 def cpp_value_to_v8_value(idl_type, cpp_value, isolate='info.GetIsolate()', creation_context='', extended_attributes=None):
     """Returns an expression that converts a C++ value to a V8 value."""
     # the isolate parameter is needed for callback interfaces
     idl_type, cpp_value = preprocess_idl_type_and_value(idl_type, cpp_value, extended_attributes)
     this_v8_conversion_type = idl_type.v8_conversion_type(extended_attributes)
     format_string = CPP_VALUE_TO_V8_VALUE[this_v8_conversion_type]
     statement = format_string.format(cpp_value=cpp_value, isolate=isolate, creation_context=creation_context)
     return statement
 
 IdlType.cpp_value_to_v8_value = cpp_value_to_v8_value