Update Gaia API documents for #8d21e3cbea1cc8515c460e1d2427e1a161812ddb
    Merge pull request #14539 from steveck-chung/message-timestamp-changes

Bug 944881 - Gaia should interpret timestamps as long-long numbers. r=julienw, a=blocking-b2g 1.3+
(cherry picked from commit 87345e3947da71386552561d5f15109955d4fe15)