Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=996329, where the m line from firefox have a space at the end.

For example:
"m=application 38233 DTLS/SCTP 5000 "

BUG=3212
TEST=manually try to use DataChannel between FF 28 and Chrome with rtccopy.com
R=jiayl@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12029005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5915 4adac7df-926f-26a2-2b94-8c16560cd09d

talk/app/webrtc/webrtcsdp.cc

@@ -2115,6 +2115,12 @@ bool ParseMediaDescription(const std::string& message,
     // <fmt>
     std::vector<int> codec_preference;
     for (size_t j = 3 ; j < fields.size(); ++j) {
+      // TODO(wu): Remove when below bug is fixed.
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=996329
+      if (fields[j] == "" && j == fields.size() - 1) {
+        continue;
+      }
+
       int pl = 0;
       if (!GetValueFromString(line, fields[j], &pl, error)) {
         return false;