Add PeerConnection::StartRtcEventLog version that takes RtcEventLogOutput as parameter

This will allow Chrome to provide a RtcEventLogOutput object that reports the log back to Chrome, allowing Chrome to manage the log by itself - write it to a file, upload it to a server, etc.

Bug: webrtc:8111
Change-Id: I6a2a6945fc8586ef10e0fb9c56eaa8fda00dfc98
Reviewed-on: https://webrtc-review.googlesource.com/8081
Commit-Queue: Elad Alon <eladalon@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20295}
diff --git a/pc/BUILD.gn b/pc/BUILD.gn
index c12c5b3..a8528ea 100644
--- a/pc/BUILD.gn
+++ b/pc/BUILD.gn
@@ -462,6 +462,7 @@
       "../api/audio_codecs:builtin_audio_encoder_factory",
       "../api/audio_codecs/L16:audio_decoder_L16",
       "../api/audio_codecs/L16:audio_encoder_L16",
+      "../logging:rtc_event_log_api",
       "../media:rtc_audio_video",
       "../media:rtc_data",  # TODO(phoglund): AFAIK only used for one sctp constant.
       "../media:rtc_media_base",