|this| cannot be an ambiguous declaration. Actual declarations are inserted
upon function scope creation, so we can simply parse as reference and it will
resolve correctly.

Change-Id: I3aaa1a2666b4caffbf8524caec7068125e10240b
Reviewed-on: https://chromium-review.googlesource.com/1251162Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56283}