Web Animations: Support animation of flood-opacity

LayoutTests/animations/interpolation/flood-opacity-interpolation.html

Index: LayoutTests/animations/interpolation/flood-opacity-interpolation.html
diff --git a/LayoutTests/animations/interpolation/letter-spacing-interpolation.html b/LayoutTests/animations/interpolation/flood-opacity-interpolation.html
similarity index 59%
copy from LayoutTests/animations/interpolation/letter-spacing-interpolation.html
copy to LayoutTests/animations/interpolation/flood-opacity-interpolation.html
index 92de286ca7773038e1a8e6998ac7b378c67b35ce..7886c19d73aaa7723845ef026e4af676d34dcbde 100755
--- a/LayoutTests/animations/interpolation/letter-spacing-interpolation.html
+++ b/LayoutTests/animations/interpolation/flood-opacity-interpolation.html
@@ -15,16 +15,17 @@
 <script src="resources/interpolation-test.js"></script>
 <script>
 assertInterpolation({
-  property: 'letter-spacing',
-  from: '-10px',
-  to: '10px'
+  property: 'flood-opacity',
+  from: '0.25',
+  to: '0.75'
 }, [
-  {at: -0.3, is: '-16px'},
-  {at: 0, is: '-10px'},
-  {at: 0.3, is: '-4px'},
-  {at: 0.6, is: '2px'},
-  {at: 1, is: '10px'},
-  {at: 1.5, is: '20px'},
+  {at: -1, is: '0'},
+  {at: -0.25, is: '0.125'},
+  {at: 0, is: '0.25'},
+  {at: 0.25, is: '0.375'},
+  {at: 1, is: '0.75'},
+  {at: 1.25, is: '0.875'},
+  {at: 2, is: '1'},
 ]);
 </script>
 </body>