Make zoom control animation duration configurable

src/objectliterals.jsdoc

@@ -217,6 +217,7 @@
 
 /**
  * @typedef {Object} ol.control.ZoomOptions
+ * @property {number|undefined} duration Animation duration. Default is 250ms.
  * @property {string|undefined} className CSS class name. Default is `ol-zoom`.
  * @property {number|undefined} delta The zoom delta applied on each click.
  * @property {Element|undefined} target Target.

src/ol/control/zoomcontrol.js

@@ -12,12 +12,6 @@ goog.require('ol.css');
 goog.require('ol.easing');
 
 
-/**
- * @define {number} Zoom duration.
- */
-ol.control.ZOOM_DURATION = 250;
-
-
 
 /**
  * Create a new control with 2 buttons, one for zoom in and one for zoom out.
@@ -62,6 +56,12 @@ ol.control.Zoom = function(opt_options) {
     target: options.target
   });
 
+  /**
+   * @type {number}
+   * @private
+   */
+  this.duration_ = goog.isDef(options.duration) ? options.duration : 250;
+
 };
 goog.inherits(ol.control.Zoom, ol.control.Control);
 
@@ -79,11 +79,13 @@ ol.control.Zoom.prototype.zoomByDelta_ = function(delta, browserEvent) {
   var view = map.getView().getView2D();
   var currentResolution = view.getResolution();
   if (goog.isDef(currentResolution)) {
-    map.beforeRender(ol.animation.zoom({
-      resolution: currentResolution,
-      duration: ol.control.ZOOM_DURATION,
-      easing: ol.easing.easeOut
-    }));
+    if (this.duration_ > 0) {
+      map.beforeRender(ol.animation.zoom({
+        resolution: currentResolution,
+        duration: this.duration_,
+        easing: ol.easing.easeOut
+      }));
+    }
     var newResolution = view.constrainResolution(currentResolution, delta);
     view.setResolution(newResolution);
   }