Return nullptr from RTCCertificate::FromPEM on failure.

webrtc/base/rtccertificate_unittest.cc

 /*
  *  Copyright 2015 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 119 matching lines @@
 
   // To PEM.
   RTCCertificatePEM orig_pem = orig->ToPEM();
   // Clone from PEM.
   scoped_refptr<RTCCertificate> clone = RTCCertificate::FromPEM(orig_pem);
   EXPECT_TRUE(clone);
   EXPECT_TRUE(*orig == *clone);
   EXPECT_EQ(orig->Expires(), clone->Expires());
 }
 
+TEST_F(RTCCertificateTest, FromPEMWithInvalidPEM) {
+  RTCCertificatePEM pem("not a valid PEM", "not a valid PEM");
+  scoped_refptr<RTCCertificate> certificate = RTCCertificate::FromPEM(pem);
+  EXPECT_FALSE(certificate);
+}
+
 }  // namespace rtc