GitLab

This CL reorganizes classes that derived from LocationArbitrator to instead
derive from LocationProvider. There was a quite a bit of overlap between the
two interfaces, and merging the two in favor of LocationProvider makes later
work with Blimp much easier.

Other work included:
*Addresses TODO to remove CreateArbitrator in favor of SetArbitratorForTest

BUG=614486, 637869

Review-Url: https://codereview.chromium.org/2226143002
Cr-Commit-Position: refs/heads/master@{#414735}