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

webrtc/pc/webrtcsdp_unittest.cc

 /*
  *  Copyright 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 3406 matching lines @@
   JsepSessionDescription jdesc_output(kDummyString);
   EXPECT_TRUE(
       SdpDeserialize(kSdpWithIceCredentialsInCandidateString, &jdesc_output));
   const IceCandidateCollection* candidates = jdesc_output.candidates(0);
   ASSERT_NE(nullptr, candidates);
   ASSERT_EQ(1, candidates->count());
   cricket::Candidate c = candidates->at(0)->candidate();
   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));
+}