Bug 1533959 [wpt PR 15682] - Add pause to wait for scroll stop in WPT pointerevent...

Bug 1533959 [wpt PR 15682] - Add pause to wait for scroll stop in WPT pointerevent touch test, a=testonly

Automatic update from web-platform-tests
Add pause to wait for scroll stop in WPT pointerevent touch test

In order to run the web-platform-tests automatically, we will use
testdriver Action API in all the wpt to simulate inputs. Here we are
changing some pointerevent touch input tests which are doing scrolling.

We are using "pause" action in the action sequence to  wait for the
scroll to stop to avoid fling and the memory leak.

Bug: 606367
Change-Id: Ic55144000c710789639e0996a3a3fab5ce3bdd42
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1503899
Commit-Queue: Lan Wei <lanwei@chromium.org>
Reviewed-by: Navid Zolghadr <nzolghadr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641698}

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wpt-commits: c8ee3ed601b1fa073fcc004433c95a988d8558bf
wpt-pr: 15682