src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/canDispose
class EditorGroupView:	private canDispose(editor: EditorInput): boolean {
		for (const groupView of this.accessor.groups) {
			if (groupView instanceof EditorGroupView && groupView.model.contains(editor, {
				strictEquals: true,		// only if this input is not shared across editor groups
				supportSideBySide: true // include side by side editor primary & secondary
			})) {
				return false;
			}
		}

		return true;
	}