Allow synthetic Tap gestures without a preceding TapDown

Allow synthetic Tap gestures without a preceding TapDown

While TapDown gestures are a typical part of the touch-gesture pipeline,
they are not required and probably even undesirable in the case of
synthetic Tap gestures (e.g., with tap disambiguation). Allow such
synthetic taps through the gesture stream validator.

BUG=414372
Committed: https://crrev.com/3c85191dc27cc4734458ff94324ffacf40f44c22
Cr-Commit-Position: refs/heads/master@{#295141}

[jdduke (slow), 2014-09-16 16:56:35]

jdduke@chromium.org changed reviewers:
+ tdresser@chromium.org

[jdduke (slow), 2014-09-16 16:56:35]

tdresser@: PTAL, thanks.

[tdresser, 2014-09-16 18:03:46]

You might want to re-read the CL title...

https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
File content/common/input/gesture_event_stream_validator.cc (right):

https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
content/common/input/gesture_event_stream_validator.cc:77: // not require a
preceding TapDown.
Can this ever happen on Aura? 
We don't do tap disambiguation.

Do we synthesize tap events anywhere else?

It would be a bit of a shame to weaken the event validation on Aura if it isn't
necessary.

[jdduke (slow), 2014-09-16 19:00:47]

On 2014/09/16 18:03:46, tdresser wrote:
> You might want to re-read the CL title...

Sigh, yeah, one of those days...

https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
File content/common/input/gesture_event_stream_validator.cc (right):

https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
content/common/input/gesture_event_stream_validator.cc:77: // not require a
preceding TapDown.
On 2014/09/16 18:03:46, tdresser wrote:
> Can this ever happen on Aura? 
> We don't do tap disambiguation.
> 
> Do we synthesize tap events anywhere else?
> 

You tell me :)

> It would be a bit of a shame to weaken the event validation on Aura if it
isn't
> necessary.

TapDown is one of those nice-to-have synthetic events that isn't quite as
critical as a PinchBegin or ScrollBegin, so I'm fairly indifferent here.

[tdresser, 2014-09-16 19:05:30]

On 2014/09/16 19:00:47, jdduke wrote:
> On 2014/09/16 18:03:46, tdresser wrote:
> > You might want to re-read the CL title...
> 
> Sigh, yeah, one of those days...
> 
>
https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
> File content/common/input/gesture_event_stream_validator.cc (right):
> 
>
https://codereview.chromium.org/572853005/diff/1/content/common/input/gesture...
> content/common/input/gesture_event_stream_validator.cc:77: // not require a
> preceding TapDown.
> On 2014/09/16 18:03:46, tdresser wrote:
> > Can this ever happen on Aura? 
> > We don't do tap disambiguation.
> > 
> > Do we synthesize tap events anywhere else?
> > 
> 
> You tell me :)
> 
> > It would be a bit of a shame to weaken the event validation on Aura if it
> isn't
> > necessary.
> 
> TapDown is one of those nice-to-have synthetic events that isn't quite as
> critical as a PinchBegin or ScrollBegin, so I'm fairly indifferent here.

Yeah, LGTM, we can always revisit if we do want to be a bit more strict on Aura.

[jdduke (slow), 2014-09-16 19:13:54]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-09-16 19:16:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/572853005/1

[commit-bot: I haz the power, 2014-09-16 21:16:53]

Committed patchset #1 (id:1) as 66e15d03a5bf4e5a11dfb3ffdffd7545472eb754

[commit-bot: I haz the power, 2014-09-16 21:17:31]

Patchset 1 (id:??) landed as
https://crrev.com/3c85191dc27cc4734458ff94324ffacf40f44c22
Cr-Commit-Position: refs/heads/master@{#295141}