Fix typo

Bug: None
Change-Id: Ic1a16a5cf023718a401404e62070203090bd3bd7
Reviewed-on: https://chromium-review.googlesource.com/c/1320214Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Zach Helfinstein <zhelfins@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608164}

chrome/browser/resources/chromeos/chromevox/testing/callback_helper.js

@@ -48,6 +48,6 @@ CallbackHelper.prototype = {
  * @private
  */
 CallbackHelper.testDone_ = this.testDone;
-// Remove testDone for public use since direclty using it conflicts with
+// Remove testDone for public use since directly using it conflicts with
 // this callback helper.
 delete this.testDone;