Fix test.

The definition of negative line indices was intentionally shifted
by one because the way VTT defines them doesn't appear to allow for
cues to be positioned at the very bottom of the screen in the case
that ANCHOR_TYPE_END is used.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=141168028

library/src/androidTest/java/com/google/android/exoplayer2/text/webvtt/WebvttDecoderTest.java

@@ -116,7 +116,7 @@ public class WebvttDecoderTest extends InstrumentationTestCase {
         Alignment.ALIGN_CENTER, 0.45f, Cue.LINE_TYPE_FRACTION, Cue.ANCHOR_TYPE_END, Cue.DIMEN_UNSET,
         Alignment.ALIGN_CENTER, 0.45f, Cue.LINE_TYPE_FRACTION, Cue.ANCHOR_TYPE_END, Cue.DIMEN_UNSET,
         Cue.TYPE_UNSET, 0.35f);
         Cue.TYPE_UNSET, 0.35f);
     assertCue(subtitle, 6, 6000000, 7000000, "This is the fourth subtitle.",
     assertCue(subtitle, 6, 6000000, 7000000, "This is the fourth subtitle.",
-        Alignment.ALIGN_CENTER, -10f, Cue.LINE_TYPE_NUMBER, Cue.TYPE_UNSET, Cue.DIMEN_UNSET,
+        Alignment.ALIGN_CENTER, -11f, Cue.LINE_TYPE_NUMBER, Cue.TYPE_UNSET, Cue.DIMEN_UNSET,
         Cue.TYPE_UNSET, Cue.DIMEN_UNSET);
         Cue.TYPE_UNSET, Cue.DIMEN_UNSET);
     assertCue(subtitle, 8, 7000000, 8000000, "This is the fifth subtitle.",
     assertCue(subtitle, 8, 7000000, 8000000, "This is the fifth subtitle.",
         Alignment.ALIGN_OPPOSITE, Cue.DIMEN_UNSET, Cue.TYPE_UNSET, Cue.TYPE_UNSET, 0.1f,
         Alignment.ALIGN_OPPOSITE, Cue.DIMEN_UNSET, Cue.TYPE_UNSET, Cue.TYPE_UNSET, 0.1f,