Add test coverage for interpolations using CSS wide keywords and neutral keyframes

LayoutTests/animations/interpolation/font-size-adjust-interpolation.html

Index: LayoutTests/animations/interpolation/font-size-adjust-interpolation.html
diff --git a/LayoutTests/animations/interpolation/font-size-adjust-interpolation.html b/LayoutTests/animations/interpolation/font-size-adjust-interpolation.html
index 92ba5c5687ba8d3a9d3713409be9346b6763d964..f22713a97c59bd9effafa5e4020687a2143da341 100644
--- a/LayoutTests/animations/interpolation/font-size-adjust-interpolation.html
+++ b/LayoutTests/animations/interpolation/font-size-adjust-interpolation.html
@@ -10,9 +10,14 @@
     src : url('../../resources/opensans/OpenSans-Regular.woff') format("woff");
 }
 
+.parent {
+    font-size-adjust: 3;
+}
+
 .target {
     display: inline-block;
     font-family: testFont;
+    font-size-adjust: 1;
 }
 
 .expected {
@@ -29,6 +34,55 @@
 <script src="resources/interpolation-test.js"></script>
 <script>
 assertInterpolation({
+  property: 'font-size-adjust',
+  from: '',
+  to: '2',
+}, [
+  {at: -2, is: '0'},
+  {at: -0.3, is: '0.7'},
+  {at: 0, is: '1'},
+  {at: 0.3, is: '1.3'},
+  {at: 0.6, is: '1.6'},
+  {at: 1, is: '2'},
+  {at: 1.5, is: '2.5'},
+]);
+
+assertNoInterpolation({
+  property: 'font-size-adjust',
+  from: 'initial',
+  to: '2',
+});
+
+assertInterpolation({
+  property: 'font-size-adjust',
+  from: 'inherit',
+  to: '2',
+}, [
+  {at: -2, is: '5'},
+  {at: -0.3, is: '3.3'},
+  {at: 0, is: '3'},
+  {at: 0.3, is: '2.7'},
+  {at: 0.6, is: '2.4'},
+  {at: 1, is: '2'},
+  {at: 1.5, is: '1.5'},
+]);
+
+assertInterpolation({
+  property: 'font-size-adjust',
+  from: 'unset',
+  to: '2',
+}, [
+  {at: -2, is: '5'},
+  {at: -0.3, is: '3.3'},
+  {at: 0, is: '3'},
+  {at: 0.3, is: '2.7'},
+  {at: 0.6, is: '2.4'},
+  {at: 1, is: '2'},
+  {at: 1.5, is: '1.5'},
+]);
+
+
+assertInterpolation({
     property: 'font-size-adjust',
     from: '0',
     to: '1.2'