Bug 1559599 - expect test 'track-webvtt-non-snap-to-lines.html' failed on Android. r=heycam

There is a weird rendering (or CSS) issue that the background box is little bit larger than the one in the test file, which causes test failure on Android.

Differential Revision: https://phabricator.services.mozilla.com/D35276

--HG--
extra : moz-landing-system : lando

testing/web-platform/meta/html/semantics/embedded-content/media-elements/track/track-element/track-webvtt-non-snap-to-lines.html.ini

@@ -1,3 +1,4 @@
 [track-webvtt-non-snap-to-lines.html]
   expected:
+    if (os == "android"): FAIL #Bug 1559599
     if (os == "win"): FAIL #Bug 1555849