Verify that correct number of arguments was passed.

tools/dom/scripts/htmldartgenerator.py

Index: tools/dom/scripts/htmldartgenerator.py
diff --git a/tools/dom/scripts/htmldartgenerator.py b/tools/dom/scripts/htmldartgenerator.py
index 0dc105415817ab79c08e15ece11bbb821d4f9215..01ef3d74dddd18c6db9b33ceff3fecd9ef2a1581 100644
--- a/tools/dom/scripts/htmldartgenerator.py
+++ b/tools/dom/scripts/htmldartgenerator.py
@@ -201,6 +201,7 @@ class HtmlDartGenerator(object):
       signatures,
       is_void,
       parameter_names,
+      number_of_required_in_dart,
       declaration,
       generate_call,
       is_optional,
@@ -245,6 +246,9 @@ class HtmlDartGenerator(object):
         elif not can_omit_type_check(test_type, i):
           checks.append('(%s is %s || %s == null)' % (
               parameter_name, test_type, parameter_name))
+        elif i > number_of_required_in_dart:
+          checks.append('?%s' % parameter_name)
+
       # There can be multiple presence checks.  We need them all since a later
       # optional argument could have been passed by name, leaving 'holes'.
       checks.extend(['!?%s' % name for name in parameter_names[argument_count:]])
@@ -300,6 +304,7 @@ class HtmlDartGenerator(object):
   def _GenerateDispatcherBody(self,
       operations,
       parameter_names,
+      number_of_required_in_dart,
       declaration,
       generate_call,
       is_optional,
@@ -318,6 +323,7 @@ class HtmlDartGenerator(object):
         [operation.arguments for operation in operations],
         operations[0].type.id == 'void',
         parameter_names,
+        number_of_required_in_dart,
         declaration,
         GenerateCall,
         IsOptional,
@@ -431,6 +437,7 @@ class HtmlDartGenerator(object):
           constructor_info.idl_args,
           False,
           [info.name for info in constructor_info.param_infos],
+          constructor_info.NumberOfRequiredInDart(),
           emitter.Format('$(METADATA)$FACTORY_KEYWORD $CTOR($PARAMS)',
             FACTORY_KEYWORD=('factory' if not custom_factory_ctr else
                 'static %s' % constructor_full_name),