Cannot pan in browser if magnification is enabled.

1. We cache some events to see if the user wants to trigger magnification. If no
   magnification is triggered we inject these events with adjusted time and down
   time to prevent subsequent transformations being confused by stale events.
   After the cached events, which always have a down, are injected we need to also
   update the down time of all subsequent non cached events.

bug:7379388

Change-Id: I41d8b831cc1016a0ee8f9c5ef5f42eb60a6f64d9