Prevent exposing Chrome OS specific methods to other platforms

This CL puts Chrome OS specific methods inside the preprocessor check
blocks to avoid exposing them to other platforms.

Test: Chrome works normally on DUT.
Change-Id: I5a42cdc0517a859bbd243390ed9153855acf975f
Reviewed-on: https://chromium-review.googlesource.com/c/1442071
Commit-Queue: Wei Lee <wtlee@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Cr-Commit-Position: refs/heads/master@{#631590}
2 files changed