GitLab

Partially revert r665168 (CL:1637649) which broke ARC Custom Tabs' UA override:
- chrome::SetAndroidOsForTabletSite() doesn't work because
there is no NavigationEntry yet.
- The removed TODO is still valid.

BUG=b:64863368
TEST=Open an ARC Custom Tab

Change-Id: Iabac4ad68b7b8452a44b9768a2637ce106b43d21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660390
Commit-Queue: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669584}