Bug 963292 - Make the EdgeSwipeDetector event forwarding work with APZC.
r=vingtetun
Merge pull request #15734 from etiennesegonzac/bug-963292-fix-edge-sentouchevent-apzc

Bug 963292 - Make the EdgeSwipeDetector event forwarding work with APZC. r=vingtetun
Bug 963716 - Bump gaiatest version to 0.21.4 and release to PyPI