Add `ol.ObjectEvent` for changes to `ol.Object` properties. Previously, `ol.Object` dispatched instances of `goog.events.Event` with type `change`. Now `ol.ObjectEvent` instances will be dispatched on property changes. The events include a `getKey` method to get the name of the property being changed. The `beforepropertychange` type event is fired before a property value changes, and the `propertychange` type event fires after the property value changes.
Reusing the iterator in a nested loop is not a good idea. And in
this case it is better to not have nested loops at all, because
we only have to create one array.
Where an enum value is used as an event type, it should be alllowercase (to follow DOM events). Property names should be ALLUPPERCASE in this case (just as camelCase and PascalCase are converted to CONSTANT_CASE).
Any event target can be used to dispatch generic goog.events.Event instances with an arbitrary type. In cases where we dispatch custom events, we should not use type values that collide with those used for generic events (at least internally). This allows listeners a better chance of knowing what kind of argument they will receive.
As subsequent change will clean up the enumeration and add a bit more consistency.
If you know ahead of time that you only want to listen for changes for a specific property, the foo:change type events can be useful. If you want to listen for changes on all properties, the change event becomes more useful if it provides information on what changed. And the beforechange event allows listeners to access values before they change.
This is another attempt to bring master closer to the
vector-api branch. In anticipation of the ability to keep track
of modifications on ol.Object through a beforechange event
(d7e4be0), we will be able to manage originals on the
application level or in a separate component outside of
ol.Feature.
