[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 a58e2fd766fa0a939d753b841e005c897ca168d1..7444f34a6d44bd5b658c781407530bcf49d13d82 100644
--- a/Source/core/rendering/style/RenderStyleConstants.h
+++ b/Source/core/rendering/style/RenderStyleConstants.h
@@ -544,6 +544,27 @@ 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;