src/vs/editor/common/viewLayout/linesLayout.ts/LinesLayout/_findLastWhitespaceBeforeLineNumber
class LinesLayout:	private _findLastWhitespaceBeforeLineNumber(lineNumber: number): number {
		lineNumber = lineNumber | 0;

		// Find the whitespace before line number
		const arr = this._arr;
		let low = 0;
		let high = arr.length - 1;

		while (low <= high) {
			const delta = (high - low) | 0;
			const halfDelta = (delta / 2) | 0;
			const mid = (low + halfDelta) | 0;

			if (arr[mid].afterLineNumber < lineNumber) {
				if (mid + 1 >= arr.length || arr[mid + 1].afterLineNumber >= lineNumber) {
					return mid;
				} else {
					low = (mid + 1) | 0;
				}
			} else {
				high = (mid - 1) | 0;
			}
		}

		return -1;
	}