Edit in JSFiddle

var lastNewlineIndex = 0;
while (true) {
    var nextNewlineIndex = content.indexOf("\n", lastNewlineIndex);
    if (nextNewlineIndex === -1) {
        if (content.length - lastNewlineIndex > WebInspector.SourceCodeTextEditor.AutoFormatMinimumLineLength)
            this.autoFormat = true;
        break;
    }
    if (nextNewlineIndex - lastNewlineIndex > WebInspector.SourceCodeTextEditor.AutoFormatMinimumLineLength) {
        this.autoFormat = true;
        break;
    }
    lastNewlineIndex = nextNewlineIndex + 1;
}