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This is the first part of adding permission guard for sensors based on Generic Sensor Framework.
There was consensus to add granular permissions for sensors here
https://github.com/w3c/sensors/issues/22

This CL adds permission name for the different sensors in the permission module.

Spec discussion : https://github.com/w3c/permissions/pull/142

BUG=606766

Review-Url: https://codereview.chromium.org/2791623004
Cr-Commit-Position: refs/heads/master@{#491303}