Allow exclusive touchmove slop regions in the TouchEventQueue

Allow exclusive touchmove slop regions in the TouchEventQueue

Aura's current slop region is boundary exclusive, whereas Android's is boundary
inclusive.  With the unified GR, both platforms will use a boundary inclusive
slop region, but until such time the TouchEventQueue should support either
model.  Allow this distinction via a configurable TouchEventQueue::Config
parameter.

BUG=354763
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=269496

[jdduke (slow), 2014-05-08 22:32:07]

Rick, PTAL.  This might be overkill, but testing is just easier without the
#ifdef sauce.

What do you think of the DCHECK for the not suppressing touchmove's when we get
a GestureScrollBegin?  The one (semi)legitimate case I can think of is if
WebView generates a synthetic GestureScroll{Begin,Update,End} sequence (e.g.,
using the zoom controls) while a touch is active... The DCHECK is still probably
fine in that case.

[Rick Byers, 2014-05-09 00:13:17]

This LGTM, thanks!

Yeah I think the DCHECK is good - a little more aggressive then what I've been
using in my testing, but I agree that it _should_ always be satisfied (and if
not, we'll learn something and change it <grin>).

Rick

[jdduke (slow), 2014-05-09 00:57:17]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-05-09 01:05:06]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jdduke@chromium.org/273933002/20001

[commit-bot: I haz the power, 2014-05-10 02:47:29]

Change committed as 269496