Merge pull request #14909 from davidflanagan/bug951932

Bug 951932: don't allow pick from Music for ringtones r=dmarcos(cherry picked from commit 8cbb66618c118aba48fd6f49b830f5f76a77e5fb)
Merge pull request #14910 from davidflanagan/bug951932-v1.3

Bug 951932: don't allow pick from Music for ringtones r=dmarcos a=fabrice