Adjust down time to prevent subsequent modules being misleading

MagnificationGestureHandler cache some events to see if users want to
trigger magnification. If no magnification is triggered we inject the
events with original down time. This causes the subsequent modules,
like GestureDetector, be misleading. For example, injecting a cached
ACTION_DOWN event may mistrigger a long click if the down time of the
event is long enough ago.

Bug: 131815497
Test: a11y CTS & unit tests
Change-Id: I19508e8ef7c91af02cdc628463d5715f6de22cd3