src/vs/editor/common/model/textModelTokens.ts/TextModelTokenization/isCheapToTokenize
class TextModelTokenization:	public isCheapToTokenize(lineNumber: number): boolean {
		if (!this._tokenizationStateStore) {
			return true;
		}

		const firstInvalidLineNumber = this._tokenizationStateStore.invalidLineStartIndex + 1;
		if (lineNumber > firstInvalidLineNumber) {
			return false;
		}

		if (lineNumber < firstInvalidLineNumber) {
			return true;
		}

		if (this._textModel.getLineLength(lineNumber) < Constants.CHEAP_TOKENIZATION_LENGTH_LIMIT) {
			return true;
		}

		return false;
	}