[Files app] ES6 class for unittest_util.js

Bug: 778674
Change-Id: I26cde7a7d5b606d7e038ae609c460e6434155c2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1599064
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Alex Danilo <adanilo@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658402}

ui/file_manager/file_manager/common/js/unittest_util.js

@@ -52,55 +52,56 @@ function assertFileEntryPathsEqual(expectedPaths, fileEntries) {
  *   recorder.assertCallCount(1);
  *   assertEquals(recorder.getListCall()[0], 'hammy');
  * </pre>
- * @constructor
  */
-function TestCallRecorder() {
-  /** @private {!Array<!Arguments>} */
-  this.calls_ = [];
+class TestCallRecorder {
+  constructor() {
+    /** @private {!Array<!Arguments>} */
+    this.calls_ = [];
+
+    /**
+     * The recording function. Bound in our constructor to ensure we always
+     * return the same object. This is necessary as some clients may make use
+     * of object equality.
+     *
+     * @type {function(*)}
+     */
+    this.callback = this.recordArguments_.bind(this);
+  }
 
   /**
-   * The recording function. Bound in our constructor to ensure we always
-   * return the same object. This is necessary as some clients may make use
-   * of object equality.
-   *
-   * @type {function(*)}
+   * Records the magic {@code arguments} value for later inspection.
+   * @private
    */
-  this.callback = this.recordArguments_.bind(this);
-}
-
-/**
- * Records the magic {@code arguments} value for later inspection.
- * @private
- */
-TestCallRecorder.prototype.recordArguments_ = function() {
-  this.calls_.push(arguments);
-};
+  recordArguments_() {
+    this.calls_.push(arguments);
+  }
 
-/**
- * Asserts that the recorder was called {@code expected} times.
- * @param {number} expected The expected number of calls.
- */
-TestCallRecorder.prototype.assertCallCount = function(expected) {
-  const actual = this.calls_.length;
-  assertEquals(
-      expected, actual,
-      'Expected ' + expected + ' call(s), but was ' + actual + '.');
-};
+  /**
+   * Asserts that the recorder was called {@code expected} times.
+   * @param {number} expected The expected number of calls.
+   */
+  assertCallCount(expected) {
+    const actual = this.calls_.length;
+    assertEquals(
+        expected, actual,
+        'Expected ' + expected + ' call(s), but was ' + actual + '.');
+  }
 
-/**
- * @return {?Arguments} Returns the {@code Arguments} for the last call,
- *    or null if the recorder hasn't been called.
- */
-TestCallRecorder.prototype.getLastArguments = function() {
-  return (this.calls_.length === 0) ? null :
-                                      this.calls_[this.calls_.length - 1];
-};
+  /**
+   * @return {?Arguments} Returns the {@code Arguments} for the last call,
+   *    or null if the recorder hasn't been called.
+   */
+  getLastArguments() {
+    return (this.calls_.length === 0) ? null :
+                                        this.calls_[this.calls_.length - 1];
+  }
 
-/**
- * @param {number} index Index of which args to return.
- * @return {?Arguments} Returns the {@code Arguments} for the call specified
- *    by indexd.
- */
-TestCallRecorder.prototype.getArguments = function(index) {
-  return (index < this.calls_.length) ? this.calls_[index] : null;
-};
+  /**
+   * @param {number} index Index of which args to return.
+   * @return {?Arguments} Returns the {@code Arguments} for the call specified
+   *    by indexd.
+   */
+  getArguments(index) {
+    return (index < this.calls_.length) ? this.calls_[index] : null;
+  }
+}