Reconsider the behavior of featureLayer.resetStyle()

[patrickarlt]

Working with a developer recently I ran into a whole bunch of issues with resetStyle() mostly that its behavior is difficult to predict. Currently it resets the style to whatever the style option on the feature layer is. This means that calling setStyle() will change the behavior of resetStyle().

What the developer was trying to do was this.

1. On hover make a feature more prominent
2. When a feature was selected make it extremely prominent
3. When a feature was selected make all other features less prominent

Using setStyle() for 3 made it impossible to use resetStyle() on the previously hovered/selected features in 1 and 2.

I think resetStyle() should always reset back to the first style ever applied to a layer rather then whatever style option is. This would make the above use case much easier and allow allow better compatibility with Esri Leaflet Renderers for scenarios like the following.

1. Load a feature layer with a complex renderer.
2. Create separate styles for when features are selected/hovered
3. When a feature is selected/hovered change styles of all other features
4. resetStyle() will now restore the original complex renderer.

@jgravois @kneemer What do you think?

[patrickarlt]

This also aligns more with L.GeoJSON https://github.com/Leaflet/Leaflet/blob/master/src/layer/GeoJSON.js#L49-L54

[kneemer]

Seems reasonable to me.

[jgravois]

agreed!

[patrickarlt]

Resolved in #516