Bug 830644 - Support WVGA and other non-HiDPI screen dimensions and resolutions
             * system [statusbar, quick settings, utility tray, notifications, sound manager]: px to rem, added background size definitions, refactorized sound manager for easy device adaptation
             * added @2x assests for system [statusbar, quick settings, utility tray, sound manager]
Merge pull request #8539 from basiclines/responsive-ui

Bug 830644 - Support WVGA and other non-HiDPI screen dimensions and resolutions