src/vs/base/browser/ui/scrollbar/scrollbarVisibilityController.ts/ScrollbarVisibilityController/ensureVisibility
class ScrollbarVisibilityController:	public ensureVisibility(): void {

		if (!this._isNeeded) {
			// Nothing to be rendered
			this._hide(false);
			return;
		}

		if (this._shouldBeVisible) {
			this._reveal();
		} else {
			this._hide(true);
		}
	}