Ensure we don't receive duplicate/old/non-UP InputEvents for Attribution

In order to align as well as we can with the concept of User Activation
on the web, we only allow recent ACTION_UP events to trigger
App to Web Attribution. I've set the limit to a conservative 10 seconds
as app launching can be very, very slow on low end devices. We also
prevent duplicate Events triggering Attribution by making sure the
event is more recent than the last one received.

Unfortunately, Android has made this API about as difficult to test as
they could, so we can't integration test these in an automated way (we
can't generate VerifiedInputEvents in tests). VerifiedMotionEvent is
also a final class, so we can't mock it for unit tests outside of
robolectric, but we don't have robolectric support for R yet in Chrome.

For now, I've written Manual tests to verify that behaviour is correct
and will follow up when possible with unit tests.

Bug: 1198308
Change-Id: I56d71cf85456b03f830e58304377245517328020
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2893008
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#882590}