Reuse the frame state viewHints array if defined

src/ol/view.js

@@ -256,10 +256,17 @@ ol.View.prototype.getCenter = function() {
 
 
 /**
+ * @param {Array.<number>=} opt_hints Destination array.
  * @return {Array.<number>} Hint.
  */
-ol.View.prototype.getHints = function() {
-  return this.hints_.slice();
+ol.View.prototype.getHints = function(opt_hints) {
+  if (opt_hints !== undefined) {
+    opt_hints[0] = this.hints_[0];
+    opt_hints[1] = this.hints_[1];
+    return opt_hints;
+  } else {
+    return this.hints_.slice();
+  }
 };