Add logging of host lookups made by TurnPort to the RtcEventLog.

webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h

Index: webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h
diff --git a/webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h b/webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h
index cb31d8f7793b664886c06be08dc4f20d59c7413d..364ccd783d3a1f48e53dc73464e6e9bb23d21d3e 100644
--- a/webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h
+++ b/webrtc/logging/rtc_event_log/mock/mock_rtc_event_log.h
@@ -76,6 +76,12 @@ class MockRtcEventLog : public RtcEventLog {
   MOCK_METHOD2(LogProbeResultSuccess, void(int id, int bitrate_bps));
   MOCK_METHOD2(LogProbeResultFailure,
                void(int id, ProbeFailureReason failure_reason));
+
+  MOCK_METHOD4(LogHostLookupResult,
+               void(const std::string& hostname,
+                    int error,
+                    const std::string& result,
+                    int64_t time_us));
 };
 
 }  // namespace webrtc