GitLab

This is a reland of d74c23a2
Original change's description:
> Make many base:: classes constexpr default constructible

Same CL but extracted scoped_refptr changes to separate CL.

>
> Bug: 800760
> Change-Id: Ib713771347283825ff53a8517b38a8abccd9d1bb
> Reviewed-on: https://chromium-review.googlesource.com/860157
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Daniel Cheng <dcheng@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#528805}

Bug: 800760
Change-Id: Ia989d978f632075c21f11cd81687f52b9e2bd2ca

TBR=dcheng@chromium.org

Change-Id: Ia989d978f632075c21f11cd81687f52b9e2bd2ca
Reviewed-on: https://chromium-review.googlesource.com/863622Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528934}