Unify processing of the cases when argument is declared optional in IDLs and is not optional in Web…

lib/dom/scripts/generator.py

Index: lib/dom/scripts/generator.py
diff --git a/lib/dom/scripts/generator.py b/lib/dom/scripts/generator.py
index 074abb64d17a69343e197c3b9eccaf895027cef4..73a283e630c1c956317d1c97fa5911962473431d 100644
--- a/lib/dom/scripts/generator.py
+++ b/lib/dom/scripts/generator.py
@@ -483,9 +483,9 @@ class IDLTypeInfo(object):
   def requires_v8_scope(self):
     return self._data.requires_v8_scope
 
-  def emit_to_native(self, emitter, idl_node, name, handle, interface_name):
+  def emit_to_native(self, emitter, idl_node, accept_null, name, handle, interface_name):
     if 'Callback' in idl_node.ext_attrs:
-      if set(['Optional', 'Callback']).issubset(idl_node.ext_attrs.keys()):
+      if accept_null:
         flag = 'DartUtilities::ConvertNullToDefaultValue'
       else:
         flag = 'DartUtilities::ConvertNone'
@@ -596,7 +596,8 @@ class DOMStringArrayTypeInfo(SequenceIDLTypeInfo):
   def __init__(self, data, item_info):
     super(DOMStringArrayTypeInfo, self).__init__('DOMString[]', data, item_info)
 
-  def emit_to_native(self, emitter, idl_node, name, handle, interface_name):
+  def emit_to_native(self, emitter, idl_node, accept_null, name, handle, interface_name):
+    assert not accept_null
     emitter.Emit(
         '\n'
         '        RefPtr<DOMStringList> $NAME = DartDOMStringList::toNative($HANDLE, exception);\n'
@@ -614,9 +615,9 @@ class PrimitiveIDLTypeInfo(IDLTypeInfo):
   def __init__(self, idl_type, data):
     super(PrimitiveIDLTypeInfo, self).__init__(idl_type, data)
 
-  def emit_to_native(self, emitter, idl_node, name, handle, interface_name):
+  def emit_to_native(self, emitter, idl_node, accept_null, name, handle, interface_name):
     function_name = 'dartTo%s' % self._capitalized_native_type()
-    if idl_node.ext_attrs.get('Optional') == 'DefaultIsNullString':
+    if accept_null:
       function_name += 'WithNullCheck'
     type = self.native_type()
     if type == 'SerializedScriptValue':