[regression] Re-add support for shift mask keys for clip group range selection
Submitted by Jeff F.T.
Assigned to Harish Fulara
In the new timeline, you can use ctrl to add/remove clips to a multi-clip selection, but the shift keys don't work. Would be nice for someone to reimplement that feature to be able to select everything between the clip where you shift-click and the opposite/diagonal extremity of selected clips.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=720332