Support WebIDL's ExtendedAttributeIdentList in the Blink parser

Source/bindings/scripts/blink_idl_parser.py

Index: Source/bindings/scripts/blink_idl_parser.py
diff --git a/Source/bindings/scripts/blink_idl_parser.py b/Source/bindings/scripts/blink_idl_parser.py
index a8defe23fe770ec5dda18ec1931f7b5664e40ce8..feed0e55d9449cbb2fd47bad4ba9b3eec350d691 100644
--- a/Source/bindings/scripts/blink_idl_parser.py
+++ b/Source/bindings/scripts/blink_idl_parser.py
@@ -333,17 +333,23 @@ class BlinkIDLParser(IDLParser):
         elif len(p) == 3:
             p[0] = ListFromConcat(self.BuildTrue('NULLABLE'), p[2])
 
-    # [b76.1] Add support for compound Extended Attribute values (A&B and A|B)
+    # [94] A=(B,C)
+    # Blink extension: OR attribute lists, A=B|C
     def p_ExtendedAttributeIdentList(self, p):
-        """ExtendedAttributeIdentList : identifier '=' identifier '&' IdentAndList
+        """ExtendedAttributeIdentList : identifier '=' '(' identifier ',' IdentifierList ')'
                                       | identifier '=' identifier '|' IdentOrList"""
-        value = self.BuildAttribute('VALUE', p[3] + p[4] + p[5])
-        p[0] = self.BuildNamed('ExtAttribute', p, 1, value)
+        if len(p) == 6:
+            value = p[3] + p[4] + p[5]
+        else:
+            value = p[4] + p[5] + p[6]
+
+        attribute = self.BuildAttribute('VALUE', value)
+        p[0] = self.BuildNamed('ExtAttribute', p, 1, attribute)
 
-    # [b76.2] A&B&C
-    def p_IdentAndList(self, p):
-        """IdentAndList : identifier '&' IdentAndList
-                        | identifier"""
+    # [89] A,B,C
+    def p_IdentifierList(self, p):
+        """IdentifierList : identifier ',' IdentifierList
+                          | identifier"""
         if len(p) > 3:
             p[0] = p[1] + p[2] + p[3]
         else: