File Manager cleanup: Use CustomEvent type parameters.

Bug: 924733
Change-Id: I2a3120f6fb9164a700be4de9aaba321426f11130
Reviewed-on: https://chromium-review.googlesource.com/c/1469282
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631516}
diff --git a/ui/file_manager/audio_player/elements/audio_player.js b/ui/file_manager/audio_player/elements/audio_player.js
index ae96d3e..bbb307a 100644
--- a/ui/file_manager/audio_player/elements/audio_player.js
+++ b/ui/file_manager/audio_player/elements/audio_player.js
@@ -422,7 +422,7 @@
   /**
    * Invoked when dragging state of seek bar on control panel is changed.
    * During the user is dragging it, audio playback is paused temporalily.
-   * @param {!{detail: {value: boolean}}} e
+   * @param {!CustomEvent<{value: boolean}>} e
    */
   onSeekingChanged_: function(e) {
     if (e.detail.value && this.playing) {
@@ -438,7 +438,7 @@
   },
 
   /**
-   * @param {!{detail: number}} e
+   * @param {!CustomEvent<number>} e
    * @private
    */
   onUpdateTime_: function(e) {
diff --git a/ui/file_manager/base/js/volume_manager_types.js b/ui/file_manager/base/js/volume_manager_types.js
index 9f71a20..1ffe8f3 100644
--- a/ui/file_manager/base/js/volume_manager_types.js
+++ b/ui/file_manager/base/js/volume_manager_types.js
@@ -411,7 +411,7 @@
  * file is newly mounted, or when opened a one already mounted.
  * @param {!DirectoryEntry} mountPoint The root directory of the mounted
  *     volume.
- * @return {!CustomEvent}
+ * @return {!CustomEvent<!DirectoryEntry>}
  */
 VolumeManagerCommon.createArchiveOpenedEvent = function(mountPoint) {
   return new CustomEvent(