Limit starting bounds of swipe to animation start rect

* If the starting point is greater than that of the current
device's width (in either positive or negative direction),
reset the starting rect to be fullscreen task bounds
* More details at b/228829958#comment12

Fixes: 228829958
Test: Reboot device and swipe up from home immediately,
app doesn't fling from the side.
Tested with portrait and landscape launcher.
Tested with fake landscape launcher.

Change-Id: I6ea24e30e9de5716b7830f487b2ed63f56598c50