Make rtc_event_log protos publicly visible.

Bug: None
Change-Id: I189f249914e0fa67826b69aacf93288aa54ac0d5
Reviewed-on: https://webrtc-review.googlesource.com/c/111254
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25689}

logging/BUILD.gn

@@ -270,6 +270,7 @@ rtc_source_set("fake_rtc_event_log") {
 
 if (rtc_enable_protobuf) {
   proto_library("rtc_event_log_proto") {
+    visibility = [ "*" ]
     sources = [
       "rtc_event_log/rtc_event_log.proto",
     ]
@@ -277,6 +278,7 @@ if (rtc_enable_protobuf) {
   }
 
   proto_library("rtc_event_log2_proto") {
+    visibility = [ "*" ]
     sources = [
       "rtc_event_log/rtc_event_log2.proto",
     ]