src/vs/workbench/contrib/search/common/searchModel.ts/SearchModel/replaceString
class SearchModel:	set replaceString(replaceString: string) {
		this._replaceString = replaceString;
		if (this._searchQuery) {
			this._replacePattern = new ReplacePattern(replaceString, this._searchQuery.contentPattern);
		}
		this._onReplaceTermChanged.fire();
	}