Fling scrolling doesn't seem to work properly in VR tests if the touchpad is released like a normal user would do. Instead, it only seems to work if we perform a quick scroll gesture, but don't release the touchpad.

This can be reproduced by patching in https://chromium-review.googlesource.com/c/chromium/src/+/874615 and running VrShellControllerInputTest#testControllerFlingScrolling.

Passing true for fling in scroll() will cause the touchpad to not be released, resulting in a fling scroll, while passing false will release the touchpad and perform a normal scroll.