IDL: make optional arguments (without default) explicit sometimes

Source/bindings/scripts/v8_methods.py

Index: Source/bindings/scripts/v8_methods.py
diff --git a/Source/bindings/scripts/v8_methods.py b/Source/bindings/scripts/v8_methods.py
index 76be0ed41c5617d14a7038f32bb86ca8e65b3a98..a112beeb9d5d41cd3d7fe3d445eb8e0e0e2f35dc 100644
--- a/Source/bindings/scripts/v8_methods.py
+++ b/Source/bindings/scripts/v8_methods.py
@@ -89,7 +89,7 @@ def method_context(interface, method):
     name = method.name
 
     idl_type.add_includes_for_type()
-    this_cpp_value = cpp_value(interface, method, len(arguments))
+    this_cpp_value = cpp_value(interface, method)
 
     def function_template():
         if is_static:
@@ -205,11 +205,14 @@ def method_context(interface, method):
 def argument_context(interface, method, argument, index):
     extended_attributes = argument.extended_attributes
     idl_type = argument.idl_type
-    this_cpp_value = cpp_value(interface, method, index)
     is_variadic_wrapper_type = argument.is_variadic and idl_type.is_wrapper_type
     return_promise = (method.idl_type.name == 'Promise' if method.idl_type
                                                         else False)
 
+    is_explicit_optional = argument.is_optional and not argument.default_value
+    if is_explicit_optional:
+        includes.add('bindings/core/v8/Optional.h')
+
     if ('ImplementedInPrivateScript' in extended_attributes and
         not idl_type.is_wrapper_type and
         not idl_type.is_basic_type):
@@ -219,13 +222,11 @@ def argument_context(interface, method, argument, index):
         'cpp_type': idl_type.cpp_type_args(extended_attributes=extended_attributes,
                                            raw_type=True,
                                            used_as_variadic_argument=argument.is_variadic),
-        'cpp_value': this_cpp_value,
+        'cpp_type_initializer': idl_type.cpp_type_initializer,
         # FIXME: check that the default value's type is compatible with the argument's
         'default_value': argument.default_cpp_value,
         'enum_validation_expression': idl_type.enum_validation_expression,
         'handle': '%sHandle' % argument.name,
-        # FIXME: remove once [Default] removed and just use argument.default_value
-        'has_default': 'Default' in extended_attributes or argument.default_value,
         'has_type_checking_interface':
             (has_extended_attribute_value(interface, 'TypeChecking', 'Interface') or
              has_extended_attribute_value(method, 'TypeChecking', 'Interface')) and
@@ -240,6 +241,7 @@ def argument_context(interface, method, argument, index):
         'index': index,
         'is_clamp': 'Clamp' in extended_attributes,
         'is_callback_interface': idl_type.is_callback_interface,
+        'is_explicit_optional': is_explicit_optional,
         'is_nullable': idl_type.is_nullable,
         'is_optional': argument.is_optional,
         'is_variadic_wrapper_type': is_variadic_wrapper_type,
@@ -248,8 +250,6 @@ def argument_context(interface, method, argument, index):
         'private_script_cpp_value_to_v8_value': idl_type.cpp_value_to_v8_value(
             argument.name, isolate='scriptState->isolate()',
             creation_context='scriptState->context()->Global()'),
-        'v8_set_return_value': v8_set_return_value(interface.name, method, this_cpp_value),
-        'v8_set_return_value_for_main_world': v8_set_return_value(interface.name, method, this_cpp_value, for_main_world=True),
         'v8_value_to_local_cpp_value': v8_value_to_local_cpp_value(argument, index, return_promise=return_promise),
         'vector_type': v8_types.cpp_ptr_type('Vector', 'HeapVector', idl_type.gc_type),
     }
@@ -269,9 +269,18 @@ def argument_declarations_for_private_script(interface, method):
 # Value handling
 ################################################################################
 
-def cpp_value(interface, method, number_of_arguments):
+def cpp_value(interface, method):
     def cpp_argument(argument):
         idl_type = argument.idl_type
+        if argument.is_optional and not argument.default_value:
+            cpp_type_optional = v8_types.cpp_template_type(
+                'Optional', idl_type.cpp_type_args(
+                    extended_attributes=argument.extended_attributes,
+                    raw_type=idl_type.preprocessed_type.is_string_type,
+                    used_in_cpp_sequence=True))
+            return '{cpp_type_optional}({name}, {name}Missing)'.format(
+                cpp_type_optional=cpp_type_optional,
+                name=argument.name)
         if idl_type.name == 'EventListener':
             return argument.name
         if (idl_type.is_callback_interface or
@@ -281,8 +290,6 @@ def cpp_value(interface, method, number_of_arguments):
             return '%s.release()' % argument.name
         return argument.name
 
-    # Truncate omitted optional arguments
-    arguments = method.arguments[:number_of_arguments]
     cpp_arguments = []
     if 'ImplementedInPrivateScript' in method.extended_attributes:
         cpp_arguments.append('toFrameIfNotDetached(info.GetIsolate()->GetCurrentContext())')
@@ -301,7 +308,7 @@ def cpp_value(interface, method, number_of_arguments):
         not 'ImplementedInPrivateScript' in method.extended_attributes and
         not method.is_static):
         cpp_arguments.append('*impl')
-    cpp_arguments.extend(cpp_argument(argument) for argument in arguments)
+    cpp_arguments.extend(cpp_argument(argument) for argument in method.arguments)
 
     this_union_arguments = method.idl_type and method.idl_type.union_arguments
     if this_union_arguments: