src/vs/base/common/scrollable.ts/Scrollable/_setState
class Scrollable:	private _setState(newState: ScrollState, inSmoothScrolling: boolean): void {
		const oldState = this._state;
		if (oldState.equals(newState)) {
			// no change
			return;
		}
		this._state = newState;
		this._onScroll.fire(this._state.createScrollEvent(oldState, inSmoothScrolling));
	}