base: Fix/add header #ifndef guards.

Header guards should be defined based on the path and file name of the
header file. Some headers have it wrong, some are missing the guards,
and some just have the matching comment wrong.

R=Nico
BUG=464816

Review URL: https://codereview.chromium.org/985003004

Cr-Commit-Position: refs/heads/master@{#319722}
49 files changed