Refactor thread_local.h's TLS Implemetation to use ThreadLocalStorage

thread_local_*'s implementation of TLS was redundant with
thread_local_storage_*'s implementation.

This change reduces the number of implementations by one.

BUG=588824

Committed: https://crrev.com/8f0b97ae15609cee6fe67d2b0b958ef37cffb1e0
Review-Url: https://codereview.chromium.org/1726203002
Cr-Original-Commit-Position: refs/heads/master@{#377774}
Cr-Commit-Position: refs/heads/master@{#424162}
6 files changed