Use <atomic> in text_encoding_registry.cc.

Bug: 736037
Change-Id: I4b4b0e221ac987f0c2de81cbc2709c7711d0d1df
Reviewed-on: https://chromium-review.googlesource.com/c/1351450
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611098}
1 file changed