Refactoring: move ownership of RtcEventLog from Call to PeerConnection

This CL is a pure refactoring which should not result in any functinal
changes. It moves ownership of the RtcEventLog from webrtc::Call to the
webrtc::PeerConnection object.

This is done so that we can add RtcEventLog support for ICE events -
which will require the TransportController to have a pointer to the
RtcEventLog. PeerConnection is the closest common owner of both Call and
TransportController (through WebRtcSession).

BUG=webrtc:6393

Review-Url: https://codereview.webrtc.org/2353033005
Cr-Commit-Position: refs/heads/master@{#14578}
diff --git a/webrtc/api/statscollector_unittest.cc b/webrtc/api/statscollector_unittest.cc
index acef448..8d5978f 100644
--- a/webrtc/api/statscollector_unittest.cc
+++ b/webrtc/api/statscollector_unittest.cc
@@ -29,6 +29,7 @@
 #include "webrtc/base/fakesslidentity.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/network.h"
+#include "webrtc/logging/rtc_event_log/rtc_event_log.h"
 #include "webrtc/media/base/fakemediaengine.h"
 #include "webrtc/media/base/test/mock_mediachannel.h"
 #include "webrtc/p2p/base/faketransportcontroller.h"
@@ -493,7 +494,8 @@
         media_controller_(
             webrtc::MediaControllerInterface::Create(cricket::MediaConfig(),
                                                      worker_thread_,
-                                                     channel_manager_.get())),
+                                                     channel_manager_.get(),
+                                                     &event_log_)),
         session_(media_controller_.get()) {
     // By default, we ignore session GetStats calls.
     EXPECT_CALL(session_, GetTransportStats(_)).WillRepeatedly(Return(false));
@@ -751,6 +753,7 @@
               srtp_crypto_suite);
   }
 
+  webrtc::RtcEventLogNullImpl event_log_;
   rtc::Thread* const worker_thread_;
   rtc::Thread* const network_thread_;
   cricket::FakeMediaEngine* media_engine_;