IDL: Support optional argument default value syntax

Source/bindings/scripts/idl_definitions.py

Index: Source/bindings/scripts/idl_definitions.py
diff --git a/Source/bindings/scripts/idl_definitions.py b/Source/bindings/scripts/idl_definitions.py
index 2230c8f6e207153d8145a7d7dca1560077f1bf7b..9ed52133763880d1dfd0a6df4546551579d168af 100644
--- a/Source/bindings/scripts/idl_definitions.py
+++ b/Source/bindings/scripts/idl_definitions.py
@@ -394,6 +394,59 @@ class IdlConstant(TypedObject):
 
 
 ################################################################################
+# Literals
+################################################################################
+
+class IdlLiteral(object):
+    def __init__(self, idl_type, value):
+        self.idl_type = idl_type
+        self.value = value
+        self.is_null = False
+
+    def __str__(self):
+        if self.idl_type == 'DOMString':
+            return 'String("%s")' % self.value
+        if self.idl_type == 'integer':
+            return '%d' % self.value
+        if self.idl_type == 'float':
+            return '%g' % self.value
+        if self.idl_type == 'boolean':
+            return 'true' if self.value else 'false'
+        raise ValueError('Unsupported literal type: %s' % self.idl_type)
+
+
+class IdlLiteralNull(IdlLiteral):
+    def __init__(self):
+        self.idl_type = 'NULL'
+        self.value = None
+        self.is_null = True
+
+    def __str__(self):
+        return 'nullptr'
+
+
+def default_node_to_idl_literal(node):
+    # FIXME: This code is unnecessarily complicated due to the rather
+    # inconsistent way the upstream IDL parser outputs default values.
+    # http://crbug.com/374178
+    idl_type = node.GetProperty('TYPE')
+    if idl_type == 'DOMString':
+        value = node.GetProperty('NAME')
+        if '"' in value or '\\' in value:
+            raise ValueError('Unsupported string value: %r' % value)
+        return IdlLiteral(idl_type, value)
+    if idl_type == 'integer':
+        return IdlLiteral(idl_type, int(node.GetProperty('NAME')))
+    if idl_type == 'float':
+        return IdlLiteral(idl_type, float(node.GetProperty('VALUE')))
+    if idl_type == 'boolean':
+        return IdlLiteral(idl_type, node.GetProperty('VALUE'))
+    if idl_type == 'NULL':
+        return IdlLiteralNull()
+    raise ValueError('Unrecognized default value type: %s' % idl_type)
+
+
+################################################################################
 # Operations
 ################################################################################
 
@@ -475,6 +528,7 @@ class IdlArgument(TypedObject):
         self.is_optional = node.GetProperty('OPTIONAL')  # syntax: (optional T)
         self.is_variadic = False  # syntax: (T...)
         self.name = node.GetName()
+        self.default_value = None
 
         children = node.GetChildren()
         for child in children:
@@ -488,6 +542,8 @@ class IdlArgument(TypedObject):
                 if child_name != '...':
                     raise ValueError('Unrecognized Argument node; expected "...", got "%s"' % child_name)
                 self.is_variadic = child.GetProperty('ELLIPSIS') or False
+            elif child_class == 'Default':
+                self.default_value = default_node_to_idl_literal(child)
             else:
                 raise ValueError('Unrecognized node class: %s' % child_class)