Do not apply rotation constraint while rotating

This is on par to what the TouchRotate interaction does.

src/ol/interaction/dragrotateinteraction.js

@@ -1,6 +1,7 @@
 goog.provide('ol.interaction.DragRotate');
 
 goog.require('ol.View2D');
+goog.require('ol.ViewHint');
 goog.require('ol.interaction.ConditionType');
 goog.require('ol.interaction.Drag');
 
@@ -46,12 +47,26 @@ ol.interaction.DragRotate.prototype.handleDrag = function(mapBrowserEvent) {
     // FIXME supports View2D only
     goog.asserts.assert(view instanceof ol.View2D);
     map.requestRenderFrame();
-    view.rotate(map, view.getRotation() - delta);
+    view.rotateNoConstraint(map, view.getRotation() - delta);
   }
   this.lastAngle_ = theta;
 };
 
 
+/**
+ * @inheritDoc
+ */
+ol.interaction.DragRotate.prototype.handleDragEnd = function(mapBrowserEvent) {
+  var browserEvent = mapBrowserEvent.browserEvent;
+  var map = mapBrowserEvent.map;
+  // FIXME supports View2D only
+  var view = map.getView();
+  goog.asserts.assert(view instanceof ol.View2D);
+  view.rotate(map, view.getRotation());
+  view.setHint(ol.ViewHint.INTERACTING, -1);
+};
+
+
 /**
  * @inheritDoc
  */
@@ -65,6 +80,7 @@ ol.interaction.DragRotate.prototype.handleDragStart =
     goog.asserts.assert(view instanceof ol.View2D);
     map.requestRenderFrame();
     this.lastAngle_ = undefined;
+    view.setHint(ol.ViewHint.INTERACTING, 1);
     return true;
   } else {
     return false;