Handle RTCCertificate::fromPEM returning nullptr, with a unit test.

content/renderer/media/rtc_certificate_generator.cc

 // Copyright (c) 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/rtc_certificate_generator.h"
 
 #include <string>
 #include <utility>
 
 #include "base/macros.h"
@@ skipping 148 matching lines @@
   return WebRTCKeyParamsToKeyParams(key_params).IsValid();
 }
 
 std::unique_ptr<blink::WebRTCCertificate> RTCCertificateGenerator::fromPEM(
     blink::WebString pem_private_key,
     blink::WebString pem_certificate) {
   rtc::scoped_refptr<rtc::RTCCertificate> certificate =
       rtc::RTCCertificate::FromPEM(
           rtc::RTCCertificatePEM(pem_private_key.utf8(),
               pem_certificate.utf8()));
-  return std::unique_ptr<blink::WebRTCCertificate>(
-      new RTCCertificate(certificate));
+  if (!certificate)
+    return nullptr;
+  return base::MakeUnique<RTCCertificate>(certificate);
 }
 
 }  // namespace content