[WebVTT] Support text-decoration-{text,color,style} on CSS ::cue pseudo-element

LayoutTests/media/track/track-css-all-cues.html

Index: LayoutTests/media/track/track-css-all-cues.html
diff --git a/LayoutTests/media/track/track-css-all-cues.html b/LayoutTests/media/track/track-css-all-cues.html
index 725cca1616196c6cf42d0206c721bfc22c24afa4..00178a6b3fce3f0d67016015016260198cb2e420 100644
--- a/LayoutTests/media/track/track-css-all-cues.html
+++ b/LayoutTests/media/track/track-css-all-cues.html
@@ -9,7 +9,15 @@
 
         <style>
 
-        video::cue { color: purple; background-color: lime; }
+        video::cue {
+            color: purple;
+            background-color: lime;
+            /* FIXME: 'text-decoration' shorthand to be handled when available.
+             * See https://chromiumcodereview.appspot.com/19516002 for details. */
+            text-decoration-line: underline;
+            text-decoration-style: dashed;
+            text-decoration-color: cyan;
+        }
 
         </style>
 
@@ -19,6 +27,9 @@
         {
             testExpected("getComputedStyle(textTrackDisplayElement(video, 'cue')).color", "rgb(128, 0, 128)");
             testExpected("getComputedStyle(textTrackDisplayElement(video, 'cue')).backgroundColor", "rgb(0, 255, 0)");
+            testExpected("getComputedStyle(textTrackDisplayElement(video, 'cue')).textDecorationLine", "underline");
+            testExpected("getComputedStyle(textTrackDisplayElement(video, 'cue')).textDecorationStyle", "dashed");
+            testExpected("getComputedStyle(textTrackDisplayElement(video, 'cue')).textDecorationColor", "rgb(0, 255, 255)");
             endTest();
         }