Bug 830644 - [wallpaper] Support WVGA and other non-HiDPI screen dimensions and resolutions
  * Added @2x wallpapers
  * px to rem conversions
  * fixed header implementation
Merge pull request #8989 from basiclines/hidpi-support-wallpaper

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