src/vs/editor/browser/view.ts/View/_createTextAreaHandlerHelper
class View:	private _createTextAreaHandlerHelper(): IVisibleRangeProvider {
		return {
			visibleRangeForPosition: (position: Position) => {
				this._flushAccumulatedAndRenderNow();
				return this._viewLines.visibleRangeForPosition(position);
			}
		};
	}