Fix touchscreen scroll inconsistency
My theory is that horizontal overshoot is needed for the touchscreen scrolling because the swipe is not a perfect vertical line and limiting the horizontal overshoot will stop the scrolling process, taking from state Pressed to Inactive, making the swipe select text instead of scrolling.
Fixing the scroll issue will make selecting impossible without some type of special long press, so I added a timer trigger of 500ms to manually transition to Inactive state. I don't know if this is the best solution, but I think it's one of the simplest. The 500ms seems to be the interval usually used by Android and IOS, not sure if there is a better constant to be used here.
You can test it without a touchscreen using the technique mentioned at !516 (merged). The bug 450440 can be reproduced at some level by doing irregular and curved vertical swipes (the issue seems to be much more common in a real touchscreen, though).