SkAR Java: minor refactoring to TapHelper (now GestureHelper)

Bug: skia:
Change-Id: I1983c6cb1727e86fec91a0c9a5706f26070b1b49
Reviewed-on: https://skia-review.googlesource.com/144021
Reviewed-by: Mike Reed <reed@google.com>
5 files changed