[Sensors] Align sensor reading updates and 'onchange' notification with rAF.

For all sensors new reading values are read and 'onchange' notfication is send from rAF callbacks, thus avoiding possible Critical Rendering Path interruption.

Before this change a timers were used and this could unnecessarily drain CPU and battery.

BUG=668052
BUG=606766

Review-Url: https://codereview.chromium.org/2551223003
Cr-Commit-Position: refs/heads/master@{#439467}
12 files changed