Compilers don't flatten os << const char* for you. Save a bit binary size.

Bug:NO

Change-Id: Iabe0de83fdf6394f223d0423e63bd5aadf1453b3
Reviewed-on: https://chromium-review.googlesource.com/503829Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
Cr-Commit-Position: refs/heads/master@{#45272}