[docs] Updated tab_helpers.md tp reflect latest class names

Change-Id: Ic96e1f9de455d93b04129fbaecf873b6c6480ac3
Reviewed-on: https://chromium-review.googlesource.com/c/1365836
Reviewed-by: Bill Orr <billorr@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Commit-Queue: Suman Kancherla <sumankancherla@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614477}
1 file changed