Gets or sets the SizeSource of the playback being edited.
Namespace: Playbacks.OptionsEditor.MultipleSelection
ActionScript.SetProperty(Playbacks.OptionsEditor.MultipleSelection.SizeSource,[value])
http://[ip]:4430/titan/get/2/Playbacks/OptionsEditor/MultipleSelection/SizeSource
POST /titan/set/2/Playbacks/OptionsEditor/MultipleSelection/SizeSource