When goog.events.listen receives an array of event types,
it only return null as listener key. So that calling
goog.events.unlistenByKey does not work.
When the event object is reference outside the call stack of the
original event handler (like in a setTimeout), accessing its
properties results in a "member not found" error. The solution is to
clone the event object and use the clone.
The other "up" type listeners (for touch and pointer) do not set this to null. This event can be of use to a click listener that might want to compare the down position to the click event's position.
The relayEvent_ method wraps goog's browser events in our MapBrowserEvent. This allows interactions to deal with real browser events in addition to our emulated events.
This commit refactors the code of the map browser event handler. The changes are the following:
Previously the `handleTouch*_` listener functions handled both `touch*` and `mspointer*` events. With this commit we use per-event type listeners. This duplicates some code (could be avoidable), but makes it easier to introduce mouse/touch/pointer specific treatments in the future.
We now listen to pointermove, pointerup, touchmove and touchend only when needed. In this way we're assured that a `down` event was received (and that `this.down_` is set) when the `up` or `move` listeners are called. This fixes the bug @oterral reported on the mailing list: https://groups.google.com/d/msg/ol3-dev/jR844F7Nlg8/eN9dt4uATK0J.
To avoid problems in browsers that trigger different types of events (e.g. both mouse and pointer events) the `down` listeners unregister the other `down` listeners. For example, the `pointerdown` listener unregisters the `mousedown` and `touchstart` listeners, for ever.
`click` events are fired only if the mouse action button is pressed. This prevents `click` events from being fired when the middle mouse button is used.
Also, without this commit, in Chrome with emulated touch events enabled, double-clicking the map doesn't zoom the map. This is because `ol.BrowserFeature.HAS_TOUCH` is `false` in that environment. The commit fixes it by testing `isMouseActionButton` on mouse devices only.
The map already emits emulated `click` and `dblclick` events on touch and pointer devices. With this commit the map emits emulated `click` and `dblclick` events on mouse devices as well.
