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Rejects characteristic.readValue if the frame is not connected or if
the frame disconnects during the operation.

The new adapter has a Health Thermometer service with a measurement interval
characteristic. We use this characteristic because it the only standard
characteristic that supports Read, Write and Notify.

Reconnection tests in follow up patch: http://crrev.com/2438963002

BUG=608538

Review-Url: https://codereview.chromium.org/2443473003
Cr-Commit-Position: refs/heads/master@{#427007}