Disable OutputE2ETest.Audio for flakiness.

TBR=dtseng@chromium.org
NOTRY=true (disabling test)

Bug: 876145
Change-Id: I689855e1c34de5735dde20e235bf1e8d09dbeb17
Reviewed-on: https://chromium-review.googlesource.com/1182784Reviewed-by: apacible <apacible@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584587}

chrome/browser/resources/chromeos/chromevox/cvox2/background/output_test.extjs

@@ -220,7 +220,8 @@ TEST_F('OutputE2ETest', 'Headings', function() {
   });
 });
 
-TEST_F('OutputE2ETest', 'Audio', function() {
+// Flaky, see https://crbug.com/876145.
+TEST_F('OutputE2ETest', 'DISABLED_Audio', function() {
   this.runWithLoadedTree('<audio src="foo.mp3" controls></audio>',
     function(root) {
       var el = root.find({role: 'button'});