Remove some small uses of linked_ptr from google_apis/.

BUG=556939

Change-Id: I20214613329c368ccc6756f28300421148653fe7
Reviewed-on: https://chromium-review.googlesource.com/c/1376811
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616700}
6 files changed