Adopt "QuickScale" double-tap drag zoom code in the GestureProvider

Adopt "QuickScale" double-tap drag zoom code in the GestureProvider

QuickScale, aka double-tap drag zoom, was added in KitKat on Android.  However,
the corresponding code in ScaleGestureDetector went unused by Chromium in the
old Java-based gesture detection pipeline. Remove the current custom code for
 double-tap drag zoom, adopting the implementation in ScaleGestureDetector.

Note that we maintain one slight difference with the Android platform: instead
of diminishing the relative scale delta as the drag focus deiviates from the
anchor, continue using a distance-invariant scale delta computation.

BUG=332418, 359615
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=261552

[jdduke (slow), 2014-04-03 17:29:21]

tdresser@: PTAL.  I had planned on landing this after the DIP change
(https://codereview.chromium.org/220063002/), but there are still a few issues
to work out with that patch, and I'm hoping this will fix a rare but real crash
(crbug.com/359615).

[tdresser, 2014-04-03 17:53:29]

https://codereview.chromium.org/200623003/diff/80001/content/common/input/web...
File content/common/input/web_input_event_traits.cc (right):

https://codereview.chromium.org/200623003/diff/80001/content/common/input/web...
content/common/input/web_input_event_traits.cc:156: if (event.type ==
WebInputEvent::GesturePinchUpdate &&
Can you add a comment explaining why the co-ordinates have to be the same? I
don't understand why this is necessary.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
File ui/events/gesture_detection/gesture_provider.cc (right):

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:145: std::abs(dy * px_to_dp_));
Do we have any justification for why Chromium and other android apps should
respond differently to this gesture? Presumably the android folks had some
reason to use this falloff approach, though I'm not sure what it would be.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:156: void
SetDoubleTapSupportEnabled(bool enabled) {
Maybe just "SetDoubleTapEnabled"?

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:191: bool
ignore_multitouch_events_;
The comment and the variable name don't line up here, do they?

Not all scaling events require multitouch.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
File ui/events/gesture_detection/gesture_provider.h (right):

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.h:74: bool
IsDoubleTapSupportedEnabled() const;
SupportedEnabled -> Supported|Enabled.

[jdduke (slow), 2014-04-03 19:28:01]

https://codereview.chromium.org/200623003/diff/80001/content/common/input/web...
File content/common/input/web_input_event_traits.cc (right):

https://codereview.chromium.org/200623003/diff/80001/content/common/input/web...
content/common/input/web_input_event_traits.cc:156: if (event.type ==
WebInputEvent::GesturePinchUpdate &&
On 2014/04/03 17:53:30, tdresser wrote:
> Can you add a comment explaining why the co-ordinates have to be the same? I
> don't understand why this is necessary.

Done.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
File ui/events/gesture_detection/gesture_provider.cc (right):

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:145: std::abs(dy * px_to_dp_));
On 2014/04/03 17:53:30, tdresser wrote:
> Do we have any justification for why Chromium and other android apps should
> respond differently to this gesture? Presumably the android folks had some
> reason to use this falloff approach, though I'm not sure what it would be.

I don't, but I can find out.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:156: void
SetDoubleTapSupportEnabled(bool enabled) {
On 2014/04/03 17:53:30, tdresser wrote:
> Maybe just "SetDoubleTapEnabled"?

Done.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.cc:191: bool
ignore_multitouch_events_;
On 2014/04/03 17:53:30, tdresser wrote:
> The comment and the variable name don't line up here, do they?
> 
> Not all scaling events require multitouch.

Oops yeah didn't notice the comment, thanks.

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
File ui/events/gesture_detection/gesture_provider.h (right):

https://codereview.chromium.org/200623003/diff/80001/ui/events/gesture_detect...
ui/events/gesture_detection/gesture_provider.h:74: bool
IsDoubleTapSupportedEnabled() const;
On 2014/04/03 17:53:30, tdresser wrote:
> SupportedEnabled -> Supported|Enabled.

Done.

[tdresser, 2014-04-03 19:33:48]

LGTM with nit.

https://codereview.chromium.org/200623003/diff/120001/content/common/input/we...
File content/common/input/web_input_event_traits.cc (right):

https://codereview.chromium.org/200623003/diff/120001/content/common/input/we...
content/common/input/web_input_event_traits.cc:156: // GesturePinchUpdate scales
can be cominbed only if they share a focal point,
cominbed.

[jdduke (slow), 2014-04-03 19:47:50]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-04-03 19:48:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jdduke@chromium.org/200623003/140001

[commit-bot: I haz the power, 2014-04-03 22:29:52]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-03 22:29:53]

Commit queue rejected this change because the description was changed
between the time the change entered the commit queue and the time it
was ready to commit. You can safely check the commit box again.

[jdduke (slow), 2014-04-03 22:35:05]

The CQ bit was checked by jdduke@chromium.org

[commit-bot: I haz the power, 2014-04-03 22:35:23]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jdduke@chromium.org/200623003/140001

[commit-bot: I haz the power, 2014-04-03 22:37:09]

Change committed as 261552