Reland "gc-plugin: Allow typdef as mixin marker in using macro"

This reverts commit c9efdb6fb26376a826151d722add7689b0af917d.

Bug: 911662
Change-Id: I78c93aceaf32850fcfecb2a714f3d9e6e0997b50
Reviewed-on: https://chromium-review.googlesource.com/c/1367728
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614693}
4 files changed