[CSS Grid Layout] Upgrade justify-content parsing to CSS3 Box Alignment spec.

Source/core/css/parser/CSSParserFastPaths.cpp

Index: Source/core/css/parser/CSSParserFastPaths.cpp
diff --git a/Source/core/css/parser/CSSParserFastPaths.cpp b/Source/core/css/parser/CSSParserFastPaths.cpp
index 37dd573ee6c8603ae20747afbb41cb7446629a96..8a5d3f11e71633b74b8612da8d2fd57de8b2e92c 100644
--- a/Source/core/css/parser/CSSParserFastPaths.cpp
+++ b/Source/core/css/parser/CSSParserFastPaths.cpp
@@ -318,9 +318,6 @@ bool CSSParserFastPaths::isValidKeywordPropertyAndValue(CSSPropertyID propertyId
         return valueID == CSSValueRow || valueID == CSSValueRowReverse || valueID == CSSValueColumn || valueID == CSSValueColumnReverse;
     case CSSPropertyFlexWrap:
         return valueID == CSSValueNowrap || valueID == CSSValueWrap || valueID == CSSValueWrapReverse;
-    case CSSPropertyJustifyContent:
-        // FIXME: Per CSS alignment, this property should accept an optional <overflow-position>. We should share this parsing code with 'justify-self'.
-        return valueID == CSSValueFlexStart || valueID == CSSValueFlexEnd || valueID == CSSValueCenter || valueID == CSSValueSpaceBetween || valueID == CSSValueSpaceAround;
     case CSSPropertyFontKerning:
         return valueID == CSSValueAuto || valueID == CSSValueNormal || valueID == CSSValueNone;
     case CSSPropertyWebkitFontSmoothing:
@@ -439,7 +436,6 @@ bool CSSParserFastPaths::isKeywordPropertyID(CSSPropertyID propertyId)
     case CSSPropertyAlignContent:
     case CSSPropertyFlexDirection:
     case CSSPropertyFlexWrap:
-    case CSSPropertyJustifyContent:
     case CSSPropertyFontKerning:
     case CSSPropertyWebkitFontSmoothing:
     case CSSPropertyWebkitLineBreak: