[Files app] ES6 class for drop_effect_and_label.js

Bug: 778674
Change-Id: I9e78661b34f5726855a933db61c6434adc2df2f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1614726
Commit-Queue: François Degros <fdegros@chromium.org>
Auto-Submit: François Degros <fdegros@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660642}

ui/file_manager/file_manager/foreground/js/drop_effect_and_label.js

@@ -15,36 +15,34 @@ const DropEffectType = {
 
 /**
  * Represents a drop effect and a label to describe it.
- *
- * @param {!DropEffectType} dropEffect
- * @param {?string} label
- * @constructor
- * @struct
  */
-function DropEffectAndLabel(dropEffect, label) {
+class DropEffectAndLabel {
   /**
-   * @private {string}
+   * @param {!DropEffectType} dropEffect
+   * @param {?string} label
    */
+  constructor(dropEffect, label) {
+    /** @private @const {!DropEffectType} */
     this.dropEffect_ = dropEffect;
 
     /**
-   * Optional description why the drop opeartion is (not) permitted.
-   *
-   * @private {?string}
+     * Optional description why the drop operation is (not) permitted.
+     * @private @const {?string}
      */
     this.label_ = label;
-}
+  }
 
-/**
- * @return {string} Returns the type of the drop effect.
+  /**
+   * @return {!DropEffectType} Returns the type of the drop effect.
    */
-DropEffectAndLabel.prototype.getDropEffect = function() {
+  getDropEffect() {
     return this.dropEffect_;
-};
+  }
 
-/**
+  /**
    * @return {?string} Returns the label. |none| if a label should not appear.
    */
-DropEffectAndLabel.prototype.getLabel = function() {
+  getLabel() {
     return this.label_;
-};
+  }
+}