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

Source/core/rendering/style/RenderStyleConstants.h

Index: Source/core/rendering/style/RenderStyleConstants.h
diff --git a/Source/core/rendering/style/RenderStyleConstants.h b/Source/core/rendering/style/RenderStyleConstants.h
index 0b1d5ec93375ad40afd10e50ca6c48dd0ea843d0..d223d3ad7890fbd1d989579aa590f9b7a01fdf44 100644
--- a/Source/core/rendering/style/RenderStyleConstants.h
+++ b/Source/core/rendering/style/RenderStyleConstants.h
@@ -170,7 +170,6 @@ enum EBoxDirection { BNORMAL, BREVERSE };
 enum EAlignContent { AlignContentFlexStart, AlignContentFlexEnd, AlignContentCenter, AlignContentSpaceBetween, AlignContentSpaceAround, AlignContentStretch };
 enum EFlexDirection { FlowRow, FlowRowReverse, FlowColumn, FlowColumnReverse };
 enum EFlexWrap { FlexNoWrap, FlexWrap, FlexWrapReverse };
-enum EJustifyContent { JustifyFlexStart, JustifyFlexEnd, JustifyCenter, JustifySpaceBetween, JustifySpaceAround };
 
 enum ETextSecurity {
     TSNONE, TSDISC, TSCIRCLE, TSSQUARE
@@ -542,6 +541,27 @@ enum ItemPositionType {
     LegacyPosition
 };
 
+enum ContentPosition {
+    ContentPositionAuto,
+    ContentPositionBaseline,
+    ContentPositionLastBaseline,
+    ContentPositionCenter,
+    ContentPositionStart,
+    ContentPositionEnd,
+    ContentPositionFlexStart,
+    ContentPositionFlexEnd,
+    ContentPositionLeft,
+    ContentPositionRight
+};
+
+enum ContentDistributionType {
+    ContentDistributionDefault,
+    ContentDistributionSpaceBetween,
+    ContentDistributionSpaceAround,
+    ContentDistributionSpaceEvenly,
+    ContentDistributionStretch
+};
+
 // Reasonable maximum to prevent insane font sizes from causing crashes on some platforms (such as Windows).
 static const float maximumAllowedFontSize = 1000000.0f;