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

Source/core/css/parser/BisonCSSParser-in.cpp

Index: Source/core/css/parser/BisonCSSParser-in.cpp
diff --git a/Source/core/css/parser/BisonCSSParser-in.cpp b/Source/core/css/parser/BisonCSSParser-in.cpp
index 22fb41507c103d8f0a9ed79227d424d0a1b62061..e25e460dfce890fe1245bef4d73077c601cf5324 100644
--- a/Source/core/css/parser/BisonCSSParser-in.cpp
+++ b/Source/core/css/parser/BisonCSSParser-in.cpp
@@ -514,9 +514,6 @@ bool isValidKeywordPropertyAndValue(CSSPropertyID propertyId, CSSValueID valueID
         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:
@@ -637,7 +634,6 @@ bool isKeywordPropertyID(CSSPropertyID propertyId)
     case CSSPropertyAlignContent:
     case CSSPropertyFlexDirection:
     case CSSPropertyFlexWrap:
-    case CSSPropertyJustifyContent:
     case CSSPropertyFontKerning:
     case CSSPropertyWebkitFontSmoothing:
     case CSSPropertyWebkitLineBreak: