Re-use CSSParser logic to parse keyframe keys

Source/core/css/CSSGrammar.y.in

Index: Source/core/css/CSSGrammar.y.in
diff --git a/Source/core/css/CSSGrammar.y.in b/Source/core/css/CSSGrammar.y.in
index 024f514addcc5349f46debf7ee0d7767cadc3d86..d437fb6d2cb4ff2522e62b038183b6f312daad29 100644
--- a/Source/core/css/CSSGrammar.y.in
+++ b/Source/core/css/CSSGrammar.y.in
@@ -141,6 +141,7 @@ inline static CSSParserValue makeOperatorValue(int value)
 %token INTERNAL_SELECTOR_SYM
 %token INTERNAL_VALUE_SYM
 %token INTERNAL_KEYFRAME_RULE_SYM
+%token INTERNAL_KEYFRAME_KEY_LIST_SYM
 %token INTERNAL_SUPPORTS_CONDITION_SYM
 %token KEYFRAMES_SYM
 %token WEBKIT_KEYFRAMES_SYM
@@ -339,6 +340,7 @@ stylesheet:
   | internal_value
   | internal_medialist
   | internal_keyframe_rule
+  | internal_keyframe_key_list
   | internal_supports_condition
   ;
 
@@ -354,6 +356,12 @@ internal_keyframe_rule:
     }
 ;
 
+internal_keyframe_key_list:
+    INTERNAL_KEYFRAME_KEY_LIST_SYM maybe_space key_list TOKEN_EOF {
+        parser->m_valueList = parser->sinkFloatingValueList($3);
+    }
+;
+
 internal_decls:
     INTERNAL_DECLS_SYM maybe_space_before_declaration declaration_list TOKEN_EOF {
         /* can be empty */