[Files.app] Add an unittest of NavigationListModel

This patch adds an unittest framework for JavaScript components. In addition, this also adds an unit test of NavigationListModel using the framework.

BUG=309946
TEST=browser_test passes
R=hashimoto@chromium.org, mtomasz@chromium.org

Review URL: https://codereview.chromium.org/48623002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232892 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232892