aura: Fix copying a touch-event in X11.

aura: Avoid copying a touch-event in X11.

There are two ways this was bad:
 * Copying a touch-release event ended up with an incorrect touch-id. This is
   because the original XEvent was releasing the slot-id associated with the
   tracking-id of the event. When the event is copied, the copied event then
   would look for a new touch-id for the same tracking id, and would end up with
   the first available touch-id, which may or may not be the same as the
   touch-id of the original native event (e.g. when second finger is released
   after first finger).
 * The copied XEvent was leaking, because set_delete_native_event was not being
   set on the TouchEvent. So every queued touch-event was leaking an Xevent.
   Yikes.

Making a copy of the native event does not provide any benefits. So avoid copying altogether.

BUG=none
TEST=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=134711

[sky, 2012-05-01 15:48:22]

LGTM