Revert of Override rtc::Event with Chromium's implementation (patchset #2...

Revert of Override rtc::Event with Chromium's implementation (patchset #2 id:20001 of https://codereview.chromium.org/2975553002/ )

Reason for revert:
Reverting temporarily until the webrtc change can be rolled with it.

Original issue's description:
> Preparation of overriding WebRTC's rtc::Event with Chromium's implementation.
> This change will give WebRTC the benefits of Chromium's checks and integration with thread and sequence runners (e.g. io and waitable checks).
>
> Followup changes include enabling the code from the WebRTC side (requires build file changes) and integrating the TaskQueue implementation in Chromium with sequence runners.
>
> BUG=689520
> NOTRY=true
>
> Review-Url: https://codereview.chromium.org/2975553002
> Cr-Commit-Position: refs/heads/master@{#486737}
> Committed: https://chromium.googlesource.com/chromium/src/+/07019da77f12dc06fd8a2e66061c8a79c90bc439

TBR=grunell@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=689520

Review-Url: https://codereview.chromium.org/2981863002
Cr-Commit-Position: refs/heads/master@{#486739}

third_party/webrtc_overrides/webrtc/rtc_base/event.cc

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "third_party/webrtc_overrides/webrtc/rtc_base/event.h"
-
-#include "base/time/time.h"
-
-namespace rtc {
-
-using base::WaitableEvent;
-
-Event::Event(bool manual_reset, bool initially_signaled)
-    : event_(manual_reset ? WaitableEvent::ResetPolicy::MANUAL
-                          : WaitableEvent::ResetPolicy::AUTOMATIC,
-             initially_signaled ? WaitableEvent::InitialState::SIGNALED
-                                : WaitableEvent::InitialState::NOT_SIGNALED) {}
-
-Event::~Event() {}
-
-void Event::Set() {
-  event_.Signal();
-}
-
-void Event::Reset() {
-  event_.Reset();
-}
-
-bool Event::Wait(int milliseconds) {
-  if (milliseconds == kForever) {
-    event_.Wait();
-    return true;
-  }
-
-  return event_.TimedWait(base::TimeDelta::FromMilliseconds(milliseconds));
-}
-
-}  // namespace rtc

third_party/webrtc_overrides/webrtc/rtc_base/event.h

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef THIRD_PARTY_WEBRTC_OVERRIDES_WEBRTC_RTC_BASE_EVENT_H_
-#define THIRD_PARTY_WEBRTC_OVERRIDES_WEBRTC_RTC_BASE_EVENT_H_
-
-#include "base/macros.h"
-#include "base/synchronization/waitable_event.h"
-
-namespace rtc {
-
-// Overrides WebRTC's internal event implementation to use Chromium's.
-class Event {
- public:
-  static const int kForever = -1;
-
-  Event(bool manual_reset, bool initially_signaled);
-  ~Event();
-
-  void Set();
-  void Reset();
-
-  // Wait for the event to become signaled, for the specified number of
-  // |milliseconds|.  To wait indefinetly, pass kForever.
-  bool Wait(int milliseconds);
-
- private:
-  base::WaitableEvent event_;
-  DISALLOW_IMPLICIT_CONSTRUCTORS(Event);
-};
-
-}  // namespace rtc
-
-#endif  // THIRD_PARTY_WEBRTC_OVERRIDES_WEBRTC_RTC_BASE_EVENT_H_