Move kApplicationLocale pref to ui/base

We need to use the pref in components, so move the pref to ui/base so it
can be accessed.

TBR=jam@chromium.org

Bug: 729596
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Iffc7c5c2f459340c14a74787defeab00c6c5589c
Reviewed-on: https://chromium-review.googlesource.com/1125143
Commit-Queue: Ran Ji <ranj@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573536}
32 files changed