Fix SDP parsing crash due to missing track ID in "a=msid".

webrtc/pc/webrtcsdp_unittest.cc

Index: webrtc/pc/webrtcsdp_unittest.cc
diff --git a/webrtc/pc/webrtcsdp_unittest.cc b/webrtc/pc/webrtcsdp_unittest.cc
index 81a5aaf4fe65634bb5bf78b66d08fe46425aeeee..85b0ca085d7667cfeb3118d4f7e854aa044fd231 100644
--- a/webrtc/pc/webrtcsdp_unittest.cc
+++ b/webrtc/pc/webrtcsdp_unittest.cc
@@ -3424,3 +3424,22 @@ TEST_F(WebRtcSdpTest, IceCredentialsInCandidateStringIgnored) {
   EXPECT_EQ("ufrag_voice", c.username());
   EXPECT_EQ("pwd_voice", c.password());
 }
+
+// Test that "a=msid" with a missing track ID is rejected and doesn't crash.
+// Regression test for:
+// https://bugs.chromium.org/p/chromium/issues/detail?id=686405

[pthatcher1, 2017/02/10 18:14:30]

Do we need a test for a missing stream id?

[Taylor Brandstetter, 2017/02/10 18:29:12]

Sure, why not.

+TEST_F(WebRtcSdpTest, DeserializeMsidAttributeWithMissingTrackId) {
+  static const char kSdpWithMissingTrackId[] =
+      "v=0\r\n"
+      "o=- 18446744069414584320 18446462598732840960 IN IP4 127.0.0.1\r\n"
+      "s=-\r\n"
+      "t=0 0\r\n"
+      "m=audio 9 RTP/SAVPF 111\r\n"
+      "c=IN IP4 0.0.0.0\r\n"
+      "a=rtpmap:111 opus/48000/2\r\n"
+      "a=msid:stream_id \r\n";
+
+  JsepSessionDescription jdesc_output(kDummyString);
+  EXPECT_FALSE(
+      SdpDeserialize(kSdpWithMissingTrackId, &jdesc_output));
+}