Only set certificate on DTLS transport if fingerprint is found in SDP.

webrtc/base/sslfingerprint.h

Index: webrtc/base/sslfingerprint.h
diff --git a/webrtc/base/sslfingerprint.h b/webrtc/base/sslfingerprint.h
index 4ffb2b0524ede20cc498298f00f8fe921de6657f..62b4bc812f01c2d9a3c5336e6c89c624654f6a87 100644
--- a/webrtc/base/sslfingerprint.h
+++ b/webrtc/base/sslfingerprint.h
@@ -15,6 +15,7 @@
 
 #include "webrtc/base/basictypes.h"
 #include "webrtc/base/copyonwritebuffer.h"
+#include "webrtc/base/rtccertificate.h"
 #include "webrtc/base/sslidentity.h"
 
 namespace rtc {
@@ -31,6 +32,10 @@ struct SSLFingerprint {
   static SSLFingerprint* CreateFromRfc4572(const std::string& algorithm,
                                            const std::string& fingerprint);
 
+  // Creates a fingerprint from a certificate, using the same digest algorithm
+  // as the certificate's signature.
+  static SSLFingerprint* CreateFromCertificate(const RTCCertificate* cert);
+
   SSLFingerprint(const std::string& algorithm,
                  const uint8_t* digest_in,
                  size_t digest_len);