Remove usage of deprecated WebRTC << overload.

Bug: webrtc:8982
Change-Id: I978e0a2544f6f71c250da9b0ec7aeb8e1a901bb9
Reviewed-on: https://chromium-review.googlesource.com/997336Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Jonas Olsson <jonasolsson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549457}

content/renderer/media/webrtc/rtc_error.cc

@@ -48,7 +48,8 @@ blink::WebRTCError ConvertToWebKitRTCError(
       // If adding a new error type, need 3 CLs: One to add the enum to webrtc,
       // one to update this mapping code, and one to start using the enum in
       // webrtc.
-      NOTREACHED() << "webrtc::RTCErrorType " << webrtc_error.type()
+      NOTREACHED() << "webrtc::RTCErrorType "
+                   << webrtc::ToString(webrtc_error.type())
                    << " not covered by switch statement.";
       break;
   }