[Sensors] Error handler in Senor class should stop the platform sensor

At the moment SensorProxy is the only source of error notification for the Sensor class instances, however soon other error notification sources will turn up (e.g. permission subsystem), so we must guarantee that stopping of a Sensor due to an error is reflected on platform side.

BUG=606766

Review-Url: https://codereview.chromium.org/2839963004
Cr-Commit-Position: refs/heads/master@{#467709}
5 files changed