(WIP) Use generator to generate externs for chrome.fileManagerPrivate API.

ui/file_manager/file_manager/background/js/volume_manager_impl.js

Index: ui/file_manager/file_manager/background/js/volume_manager_impl.js
diff --git a/ui/file_manager/file_manager/background/js/volume_manager_impl.js b/ui/file_manager/file_manager/background/js/volume_manager_impl.js
index 72880362d4dcc199a83399c644dc7a476a259451..c19c74e90160cb9d01c849d51598fcb1ade772e3 100644
--- a/ui/file_manager/file_manager/background/js/volume_manager_impl.js
+++ b/ui/file_manager/file_manager/background/js/volume_manager_impl.js
@@ -70,7 +70,7 @@ VolumeManagerImpl.prototype.__proto__ = cr.EventTarget.prototype;
 /**
  * Adds new volume info from the given volumeMetadata. If the corresponding
  * volume info has already been added, the volumeMetadata is ignored.
- * @param {!VolumeMetadata} volumeMetadata
+ * @param {!chrome.fileManagerPrivate.VolumeMetadata} volumeMetadata
  * @return {!Promise<!VolumeInfo>}
  * @private
  */
@@ -160,7 +160,7 @@ VolumeManagerImpl.prototype.initialize_ = function(callback) {
 
 /**
  * Event handler called when some volume was mounted or unmounted.
- * @param {MountCompletedEvent} event Received event.
+ * @param {chrome.fileManagerPrivate.MountCompletedEvent} event Received event.
  * @private
  */
 VolumeManagerImpl.prototype.onMountCompleted_ = function(event) {