src/vs/base/browser/ui/list/listWidget.ts/List/focusPreviousPage
class List:	async focusPreviousPage(browserEvent?: UIEvent, filter?: (element: T) => boolean): Promise<void> {
		let firstPageIndex: number;
		const scrollTop = this.view.getScrollTop();

		if (scrollTop === 0) {
			firstPageIndex = this.view.indexAt(scrollTop);
		} else {
			firstPageIndex = this.view.indexAfter(scrollTop - 1);
		}

		const firstPageElement = this.view.element(firstPageIndex);
		const currentlyFocusedElement = this.getFocusedElements()[0];

		if (currentlyFocusedElement !== firstPageElement) {
			const firstGoodPageIndex = this.findNextIndex(firstPageIndex, false, filter);

			if (firstGoodPageIndex > -1 && currentlyFocusedElement !== this.view.element(firstGoodPageIndex)) {
				this.setFocus([firstGoodPageIndex], browserEvent);
			} else {
				this.setFocus([firstPageIndex], browserEvent);
			}
		} else {
			const previousScrollTop = scrollTop;
			this.view.setScrollTop(scrollTop - this.view.renderHeight);

			if (this.view.getScrollTop() !== previousScrollTop) {
				this.setFocus([]);

				// Let the scroll event listener run
				await timeout(0);
				await this.focusPreviousPage(browserEvent, filter);
			}
		}
	}