src/vs/base/browser/ui/actionbar/actionbar.ts/ActionBar/focusPrevious
class ActionBar:	protected focusPrevious(): boolean {
		if (typeof this.focusedItem === 'undefined') {
			this.focusedItem = 0;
		} else if (this.viewItems.length <= 1) {
			return false;
		}

		const startIndex = this.focusedItem;
		let item: IActionViewItem;

		do {
			this.focusedItem = this.focusedItem - 1;
			if (this.focusedItem < 0) {
				if (this.options.preventLoopNavigation) {
					this.focusedItem = startIndex;
					return false;
				}

				this.focusedItem = this.viewItems.length - 1;
			}
			item = this.viewItems[this.focusedItem];
		} while (this.focusedItem !== startIndex && this.options.focusOnlyEnabledItems && !item.isEnabled());


		this.updateFocus(true);
		return true;
	}