WebRTC expects SDP to follow RFC 4566, which mandates that each line ends with CRLF (\r\n), Just add \r\n at the end of every line. For ex-
"v=0\r\n" +
"o=- 0 0 IN IP4 127.0.0.1\r\n" +
"s=-\r\n" +
"t=0 0\r\n" +
"a=group:BUNDLE 0 1\r\n" + ..............