Deprecate use of user gestures during scroll-related touch events

Deprecate use of user gestures during scroll-related touch events

See https://docs.google.com/document/d/1oF1T3O7_E4t1PYHV6gyCwHxOi3ystm0eSL5xZu7nvOg/edit#heading=h.qq59ev3u8fba

Intent to deprecate: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/2cvwbgZOZZs

This also contains a small tweak to the semantics of the TouchScrollStarted event to trigger it only on the first GestureScrollUpdate (so that it's not triggered when the page consumes all touchmove events).

BUG=611981
Review-Url: https://codereview.chromium.org/1996143002
Cr-Commit-Position: refs/heads/master@{#396215}
(cherry picked from commit adbb8a0133bf42306ac4a533a5478529e5d87895)

Committed: https://chromium.googlesource.com/chromium/src/+/34f0006c461c94b01317c5521140f995cec1badc

[Rick Byers, 2016-05-30 16:06:45]

Description was changed from

==========
Deprecate use of user gestures during scroll-related touch events

See
https://docs.google.com/document/d/1oF1T3O7_E4t1PYHV6gyCwHxOi3ystm0eSL5xZu7nv...

Intent to deprecate:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/2cvwbgZOZZs

This also contains a small tweak to the semantics of the TouchScrollStarted
event to trigger it only on the first GestureScrollUpdate (so that it's not
triggered when the page consumes all touchmove events).

BUG=611981

Review-Url: https://codereview.chromium.org/1996143002
Cr-Commit-Position: refs/heads/master@{#396215}
(cherry picked from commit adbb8a0133bf42306ac4a533a5478529e5d87895)
==========

to

==========
Deprecate use of user gestures during scroll-related touch events

See
https://docs.google.com/document/d/1oF1T3O7_E4t1PYHV6gyCwHxOi3ystm0eSL5xZu7nv...

Intent to deprecate:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/2cvwbgZOZZs

This also contains a small tweak to the semantics of the TouchScrollStarted
event to trigger it only on the first GestureScrollUpdate (so that it's not
triggered when the page consumes all touchmove events).

BUG=611981

Review-Url: https://codereview.chromium.org/1996143002
Cr-Commit-Position: refs/heads/master@{#396215}
(cherry picked from commit adbb8a0133bf42306ac4a533a5478529e5d87895)

Committed:
https://chromium.googlesource.com/chromium/src/+/34f0006c461c94b01317c5521140...
==========

[Rick Byers, 2016-05-30 16:06:46]

Committed patchset #1 (id:1) manually as
34f0006c461c94b01317c5521140f995cec1badc.