Controlling this event is necessary because (internally) we only want to process it once, even when it's tied to several marks. This typically happens on the crosshair mark which uses the same shared pointer transform on its submarks, where not controlling this would result in an even number of flag toggling — when we just want one.

However for some applications the upstream app also wants to see that event.

In this PR, instead of preventing propagation, we ignore internal duplicate handling.

closes #2052

cc: @jheer

For more context see commit 8174cfa3 as part of PR #1527.