Bug 907700 - [HD][Usage] Update subtext
Revert "Bug 990047 - Add a shared function to load JSON files and use it throughout gaia to replace the existing ad-hoc functions" for gaia unit test failures

This reverts commit 75d11a3dbf561b99bfce65a9822f2809cd91022e.
Merge pull request #22719 from pacorampas/907700

Bug 907700 - [HD][Usage] Update subtext r=mri
Bug 1053964 - [Messages][Tests] Add marionette JS test case to verify close\back button behaviour when app is in activity mode. r=schung, julien