Do not use overloaded toDartValue for primitive types.

lib/dom/scripts/systemnative.py

Index: lib/dom/scripts/systemnative.py
diff --git a/lib/dom/scripts/systemnative.py b/lib/dom/scripts/systemnative.py
index 1bb37dababd0662acf49a120d7935b6d55c6a9ac..13445af9b29852a8feaf122623dab99ee6aed73a 100644
--- a/lib/dom/scripts/systemnative.py
+++ b/lib/dom/scripts/systemnative.py
@@ -70,9 +70,11 @@ class NativeImplementationSystem(System):
       if operation.type.id == 'void':
         return_type = 'void'
         return_prefix = ''
+        error_return = ''
       else:
         return_type = 'bool'
         return_prefix = 'return '
+        error_return = ' false'
 
       parameters = []
       arguments = []
@@ -80,7 +82,7 @@ class NativeImplementationSystem(System):
         argument_type_info = GetIDLTypeInfo(argument.type.id)
         parameters.append('%s %s' % (argument_type_info.parameter_type(),
                                      argument.id))
-        arguments.append(argument.id)
+        arguments.append(argument_type_info.to_dart_conversion(argument.id))
         cpp_impl_includes |= set(argument_type_info.conversion_includes())
 
       cpp_header_handlers_emitter.Emit(
@@ -92,11 +94,16 @@ class NativeImplementationSystem(System):
           '\n'
           '$TYPE $CLASS_NAME::handleEvent($PARAMETERS)\n'
           '{\n'
+          '    if (!m_callback.isolate()->isAlive())\n'
+          '        return$ERROR_RETURN;\n'
+          '    DartIsolate::Scope scope(m_callback.isolate());\n'
+          '    DartApiScope apiScope;\n'
           '    $(RETURN_PREFIX)m_callback.handleEvent($ARGUMENTS);\n'
           '}\n',
           TYPE=return_type,
           CLASS_NAME=class_name,
           PARAMETERS=', '.join(parameters),
+          ERROR_RETURN=error_return,
           RETURN_PREFIX=return_prefix,
           ARGUMENTS=', '.join(arguments))