Replace some usage of EventWrapper with rtc::Event.

Bug: webrtc:3380
Change-Id: Id33b19bf107273e6f838aa633784db73d02ae2c2
Reviewed-on: https://webrtc-review.googlesource.com/c/107888
Reviewed-by: Henrik Grunell <henrikg@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Oskar Sundbom <ossu@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25407}

modules/utility/source/process_thread_impl.h

@@ -19,11 +19,11 @@
 #include "modules/include/module.h"
 #include "modules/utility/include/process_thread.h"
 #include "rtc_base/criticalsection.h"
+#include "rtc_base/event.h"
 #include "rtc_base/location.h"
 #include "rtc_base/platform_thread.h"
 #include "rtc_base/task_queue.h"
 #include "rtc_base/thread_checker.h"
-#include "system_wrappers/include/event_wrapper.h"
 
 namespace webrtc {
 
@@ -75,7 +75,7 @@ class ProcessThreadImpl : public ProcessThread {
   rtc::CriticalSection lock_;  // Used to guard modules_, tasks_ and stop_.
 
   rtc::ThreadChecker thread_checker_;
-  const std::unique_ptr<EventWrapper> wake_up_;
+  rtc::Event wake_up_;
   // TODO(pbos): Remove unique_ptr and stop recreating the thread.
   std::unique_ptr<rtc::PlatformThread> thread_;