[CSS Grid Layout] Adapting align-self, align-items and justify-self to the last CSS 3 spec.

LayoutTests/fast/css/getComputedStyle/resources/property-names.js

 // We only test properties that are exposed in all ports.
 var propertiesToTest = {
     "-webkit-animation-delay": true,
     "-webkit-animation-direction": true,
     "-webkit-animation-duration": true,
     "-webkit-animation-fill-mode": true,
     "-webkit-animation-iteration-count": true,
     "-webkit-animation-name": true,
     "-webkit-animation-play-state": true,
     "-webkit-animation-timing-function": true,
@@ skipping 152 matching lines @@
     "font-size": true,
     "font-style": true,
     "font-variant": true,
     "font-variant-ligatures": true,
     "font-weight": true,
     "glyph-orientation-horizontal": true,
     "glyph-orientation-vertical": true,
     "height": true,
     "image-rendering": true,
     "justify-content": true,
+    "justify-items": true,
+    "justify-self": true,
     "left": true,
     "letter-spacing": true,
     "lighting-color": true,
     "line-height": true,
     "list-style-image": true,
     "list-style-position": true,
     "list-style-type": true,
     "margin-bottom": true,
     "margin-left": true,
     "margin-right": true,
@@ skipping 66 matching lines @@
 // There properties don't show up when iterating a computed style object,
 // but we do want to dump their values in tests.
 var hiddenComputedStyleProperties = [
     "background-position-x",
     "background-position-y",
     "border-spacing",
     "overflow",
     "-webkit-mask-position-x",
     "-webkit-mask-position-y",
 ];