Fix/suppress new warnings introduced in Chromium roll.

TBR=henrika@webrtc.org

Bug: webrtc:6597
Change-Id: Id26945a7be05250673b58de8220f78bc62886688
Reviewed-on: https://webrtc-review.googlesource.com/16860
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20477}

sdk/android/api/org/webrtc/PeerConnection.java

@@ -171,6 +171,7 @@ public class PeerConnection {
       this.tlsEllipticCurves = tlsEllipticCurves;
     }
 
+    @Override
     public String toString() {
       return urls + " [" + username + ":" + password + "] [" + tlsCertPolicy + "] [" + hostname
           + "] [" + tlsAlpnProtocols + "] [" + tlsEllipticCurves + "]";