src/vs/base/browser/ui/selectBox/selectBoxCustom.ts/SelectBoxList/onPageUp
class SelectBoxList:	private onPageUp(e: StandardKeyboardEvent): void {
		dom.EventHelper.stop(e);

		this.selectList.focusPreviousPage();

		// Allow scrolling to settle
		setTimeout(() => {
			this.selected = this.selectList.getFocus()[0];

			// Shift selection down if we land on a disabled option
			if (this.options[this.selected].isDisabled && this.selected < this.options.length - 1) {
				this.selected++;
				this.selectList.setFocus([this.selected]);
			}
			this.selectList.reveal(this.selected);
			this.select(this.selected);
		}, 1);
	}