ENYO-573: Synchronize up/down events based on button.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
ENYO-573: Adding in-line documentation.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
Merge pull request #949 from enyojs/ENYO-573-aarontam

ENYO-573: Synchronize up/down events based on button.

Reviewed-By: Krishna Rangarajan (krishna.rangarajan@lge.com)
Integrated-By: Gray Norton (gray.norton@lge.com)