Increase Web Bluetooth device scanning duration [merge to M56]

This CL increases the Web Bluetooth device scanning duration from 10
seconds to 60 seconds. Also added UMA for the event that the re-scan
link is pressed and the duration to find at lease one Bluetooth device.

BUG=419413, 647100

Review-Url: https://codereview.chromium.org/2506163002
Cr-Commit-Position: refs/heads/master@{#433074}
(cherry picked from commit acdbb3c267d8d4ea19d0faf4ef34b5179f3c58fa)

Review URL: https://codereview.chromium.org/2515293003 .

Cr-Commit-Position: refs/branch-heads/2924@{#29}
Cr-Branched-From: 3a87aecc31cd1ffe751dd72c04e5a96a1fc8108a-refs/heads/master@{#433059}
4 files changed