Added debugMe method.

ui/file_manager/file_manager/background/js/volume_manager.js

Index: ui/file_manager/file_manager/background/js/volume_manager.js
diff --git a/ui/file_manager/file_manager/background/js/volume_manager.js b/ui/file_manager/file_manager/background/js/volume_manager.js
index 41a0c52ed7be60ab1d352fcc7150c34cf57aee72..9e3f2aa35858077f0d35b45f0ee2d6aa27dfb91d 100644
--- a/ui/file_manager/file_manager/background/js/volume_manager.js
+++ b/ui/file_manager/file_manager/background/js/volume_manager.js
@@ -518,6 +518,16 @@ VolumeManager.getInstanceQueue_ = new AsyncUtil.Queue();
 VolumeManager.instance_ = null;
 
 /**
+ * Returns instance of VolumeManager for debug purpose.
+ * This method returns VolumeManager.instance_ which may not be initialized.
+ *
+ * @return {VolumeManager} Volume manager.
+ */
+VolumeManager.getInstanceForDebug = function() {
+  return VolumeManager.instance_;
+};
+
+/**
  * @type {Promise}
  * @private
  */
@@ -871,6 +881,16 @@ VolumeManager.prototype.invokeRequestCallbacks_ = function(
 };
 
 /**
+ * Returns current state of VolumeManager.
+ * @return {string} Current state of VolumeManager.
+ */
+VolumeManager.prototype.toString = function() {
+  return 'VolumeManager\n' +
+      '- MountQueue_:\n' +
+      '  ' + this.mountQueue_.toString().replace(/\n/g, '\n  ');

[mtomasz, 2014/10/28 06:09:03]

nit: What's the purpose of this regular expression?

[yawano, 2014/10/28 06:11:50]

This is for indenting with two spaces.

e.g. 
A\n
B\n
C

is replaced with

A\n
  B\n
  C

+};
+
+/**
  * Location information which shows where the path points in FileManager's
  * file system.
  *