src/vs/workbench/api/common/extHostQuickOpen.ts/ExtHostQuickInput/buttons
class ExtHostQuickInput:		set buttons(buttons: QuickInputButton[]) {
			this._buttons = buttons.slice();
			this._handlesToButtons.clear();
			buttons.forEach((button, i) => {
				const handle = button === QuickInputButtons.Back ? -1 : i;
				this._handlesToButtons.set(handle, button);
			});
			this.update({
				buttons: buttons.map<TransferQuickInputButton>((button, i) => {
					return {
						...getIconPathOrClass(button),
						tooltip: button.tooltip,
						handle: button === QuickInputButtons.Back ? -1 : i,
					};
				})
			});
		}