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- Split GetApplicationLocaleInternal() so it's more readable.
- Use more C++11 features.
- Fit nits and lint errors.

Change-Id: Iff2e9b3fce4622891ebb39ace03c64d1e7603d2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1918163Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721912}