Move touchstart preventDefault to ol.renderer.dom.Map

[fredj]

preventDefault is called to prevent the img context menu on mobile devices.

Fixes #2853

[fredj]

The changes included in this PR does not fixes the issue but minimize the problem: it now only occurs when the renderer is dom and on touch device.

[elemoine]

Is it only for touch devices? I'm wondering about ie10 and the surface device. @oterral do you have any idea?

[oterral]

I can test. I'll give you the feedback this morning.

[fredj]

Thanks a lot @oterral. To test this, open the side-by-side example and long press the three maps: no context menu must appear.

[oterral]

LGTM tested on Surface/win 8.1/IE11 and PC/win 8/IE10

Long press on Surface triggers a contextmenu event so everthing works as before.

[fredj]

can we merge this one?

[elemoine]

I think there is a goog.event.preventDefault static function that you can use as the listener.

[fredj]

Good point, fixed.

[elemoine]

Also, map renderers are disposable objects, so it may make sense to implement disposeInternal and unregisters the listener there. (Sorry that up just came up to me.)

[fredj]

Let's merge this!