Divide volume_manager.js into files for each classes and extract interfaces from them.

ui/file_manager/externs/entry_location.js

Index: ui/file_manager/externs/entry_location.js
diff --git a/ui/file_manager/externs/entry_location.js b/ui/file_manager/externs/entry_location.js
new file mode 100644
index 0000000000000000000000000000000000000000..24a1d7d17caeb93dc3f3d53404f655aa89b1e41e
--- /dev/null
+++ b/ui/file_manager/externs/entry_location.js
@@ -0,0 +1,48 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * Location information which shows where the path points in FileManager's
+ * file system.
+ * @interface
+ */
+function EntryLocation() {};
+
+/**
+ * Volume information.
+ * @type {!VolumeInfo}
+ */
+EntryLocation.prototype.volumeInfo;
+
+/**
+ * Root type.
+ * @type {VolumeManagerCommon.RootType}
+ */
+EntryLocation.prototype.rootType;
+
+/**
+ * Whether the entry is root entry or not.
+ * @type {boolean}
+ */
+EntryLocation.prototype.isRootEntry;
+
+/**
+ * Whether the location obtained from the fake entry corresponds to special
+ * searches.
+ * @type {boolean}
+ */
+EntryLocation.prototype.isSpecialSearchRoot;
+
+/**
+ * Whether the location is under Google Drive or a special search root which
+ * represents a special search from Google Drive.
+ * @type {boolean}
+ */
+EntryLocation.prototype.isDriveBased;
+
+/**
+ * Whether the entry is read only or not.
+ * @type {boolean}
+ */
+EntryLocation.prototype.isReadOnly;