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Adds mobile responsive device list to bluetooth internals page.
Lists device name, address, and latest RSSI.
Refreshes when devices are discovered, removed, or advertising packets are received.

Screenshots
Desktop: https://goo.gl/photos/bot7JsdTuf8P2A328
Mobile: https://goo.gl/photos/G9bb9s4ih5KT3PJw8

BUG=651282
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2418343002
Cr-Commit-Position: refs/heads/master@{#427261}