Add default constructor for rtc::Event

Bug: webrtc:9962
Change-Id: Icaa91e657e6881fcb1553f354c07866109a0ea68
Reviewed-on: https://webrtc-review.googlesource.com/c/109500
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25535}
diff --git a/rtc_base/rate_limiter_unittest.cc b/rtc_base/rate_limiter_unittest.cc
index 6efea54..ac0625f 100644
--- a/rtc_base/rate_limiter_unittest.cc
+++ b/rtc_base/rate_limiter_unittest.cc
@@ -112,9 +112,7 @@
 class ThreadTask {
  public:
   explicit ThreadTask(RateLimiter* rate_limiter)
-      : rate_limiter_(rate_limiter),
-        start_signal_(false, false),
-        end_signal_(false, false) {}
+      : rate_limiter_(rate_limiter) {}
   virtual ~ThreadTask() {}
 
   void Run() {