src/vs/editor/common/tokens/lineTokens.ts/SliceLineTokens/constructor
class SliceLineTokens:	constructor(source: LineTokens, startOffset: number, endOffset: number, deltaOffset: number) {
		this._source = source;
		this._startOffset = startOffset;
		this._endOffset = endOffset;
		this._deltaOffset = deltaOffset;
		this._firstTokenIndex = source.findTokenIndexAtOffset(startOffset);

		this._tokensCount = 0;
		for (let i = this._firstTokenIndex, len = source.getCount(); i < len; i++) {
			const tokenStartOffset = source.getStartOffset(i);
			if (tokenStartOffset >= endOffset) {
				break;
			}
			this._tokensCount++;
		}
	}