Fix browser compatibility regressions in release-3.0.x.
Review Request #9063 - Created July 8, 2017 and submitted
Some of the new features in Review Board 3.0 regressed support for some
const, and an expectation that
Blobwas a valid type.
consthas been replaced with a
varstatement, and the
now checked as a valid type before use. This restores IE9 and some
Tested that IE9 no longer broke on page load.