File Manager: Fix a JavaScript error with unmounting using eject button.

BUG=chromium-os:30150
TEST=Test unmounting a SD card and an archive file using eject button.

Review URL: https://chromiumcodereview.appspot.com/10178036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@134447 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/file_manager/js/file_manager.js

@@ -2621,7 +2621,7 @@ FileManager.prototype = {
             return;
           }
           // Current directory just unmounted. Move to the 'Downloads'.
-          changeDirectoryTo = this.directoryModel_.getDefaultDirectory();
+          changeDirectoryTo = self.directoryModel_.getDefaultDirectory();
         }
       }