Also I think ideally the element receives move events even outside of its boundaries if the click started on it, this will be useful (necessary?) for drag scrolling, and probably other things.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f27364c1edd576aa4c366cc58e84320e5fa0a93c

commit f27364c1edd576aa4c366cc58e84320e5fa0a93c
Author: Aldo Culquicondor <acondor@chromium.org>
Date: Thu Jun 07 15:22:13 2018

VR: Locking hover events to the clicked element

This change reverts back to only sending hover events to a clicked element. This is a step towards pinning behavior.

Also, the input handling processing order is now the following:
1. Process all end/leave events.
2. Process all update/move events.
3. Process all begin/enter events.
This scheme is more robust when handling several events within a single frame.

Bug:  848733 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr
Change-Id: I2d4da5234a4b60a00849bee4462fd676eccd80b6
Reviewed-on: https://chromium-review.googlesource.com/1082601
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Commit-Queue: Aldo Culquicondor <acondor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565271}
[modify] https://crrev.com/f27364c1edd576aa4c366cc58e84320e5fa0a93c/chrome/browser/vr/ui_input_manager.cc
[modify] https://crrev.com/f27364c1edd576aa4c366cc58e84320e5fa0a93c/chrome/browser/vr/ui_input_manager.h
[modify] https://crrev.com/f27364c1edd576aa4c366cc58e84320e5fa0a93c/chrome/browser/vr/ui_input_manager_unittest.cc