The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6715a07436e4d17126c3d5d3c9775d53d025a8ba

commit 6715a07436e4d17126c3d5d3c9775d53d025a8ba
Author: Mike Wasserman <msw@chromium.org>
Date: Thu Sep 21 18:20:25 2017

mash: Support shelf item selection via ET_GESTURE_TAP.

Add basic Mojo struct traits support & test for tap gestures.
(this is the minimum needed for tapping on shelf items)

Warn and bail on sending unsupported event types.
(otherwise it's tough to track these problems down)

Bug:  766783 , 767087
Test: Chrome OS shelf items launch via touch w/ about:flags Enable shelf model synchronization"
Change-Id: I2aa813be94ce321897838c2e62de5d3097ac04ca
Reviewed-on: https://chromium-review.googlesource.com/675581
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503514}
[modify] https://crrev.com/6715a07436e4d17126c3d5d3c9775d53d025a8ba/ui/events/mojo/event.mojom
[modify] https://crrev.com/6715a07436e4d17126c3d5d3c9775d53d025a8ba/ui/events/mojo/event_constants.mojom
[modify] https://crrev.com/6715a07436e4d17126c3d5d3c9775d53d025a8ba/ui/events/mojo/event_struct_traits.cc
[modify] https://crrev.com/6715a07436e4d17126c3d5d3c9775d53d025a8ba/ui/events/mojo/event_struct_traits.h
[modify] https://crrev.com/6715a07436e4d17126c3d5d3c9775d53d025a8ba/ui/events/mojo/struct_traits_unittest.cc

My use case is satisfied with ET_GESTURE_TAP; re-targeting for other gesture events.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0

commit 9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0
Author: Kevin McNee <mcnee@chromium.org>
Date: Mon Jan 07 21:35:36 2019

Serialize touchpad pinch ui::Events

We extend the mojo struct traits for ui gesture events enough to allow
for touchpad pinch events to be serialized.

Bug: 767087, 916946
Change-Id: Ic572704a78da71c262e8e892c3023c2f5b29779d
Reviewed-on: https://chromium-review.googlesource.com/c/1394996
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620480}
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/event.mojom
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/event.typemap
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/event_constants.mojom
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/event_struct_traits.cc
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/event_struct_traits.h
[modify] https://crrev.com/9fcc0de1c33c4634e68b3e2a76560e4dc35f56f0/ui/events/mojo/struct_traits_unittest.cc