Use WaitableEvents to wake up sync IPC waiting

ipc/mojo_event.cc

-// Copyright 2016 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 "ipc/mojo_event.h"
-
-namespace IPC {
-
-MojoEvent::MojoEvent() {
-  mojo::MessagePipe pipe;
-  signal_handle_ = std::move(pipe.handle0);
-  wait_handle_ = std::move(pipe.handle1);
-}
-
-MojoEvent::~MojoEvent() {}
-
-void MojoEvent::Signal() {
-  base::AutoLock lock(lock_);
-  if (is_signaled_)
-    return;
-  is_signaled_ = true;
-  MojoResult rv = mojo::WriteMessageRaw(
-      signal_handle_.get(), nullptr, 0, nullptr, 0,
-      MOJO_WRITE_MESSAGE_FLAG_NONE);
-  CHECK_EQ(rv, MOJO_RESULT_OK);
-}
-
-void MojoEvent::Reset() {
-  base::AutoLock lock(lock_);
-  if (!is_signaled_)
-    return;
-  is_signaled_ = false;
-  MojoResult rv = mojo::ReadMessageRaw(
-      wait_handle_.get(), nullptr, nullptr, nullptr, nullptr,
-      MOJO_READ_MESSAGE_FLAG_NONE);
-  CHECK_EQ(rv, MOJO_RESULT_OK);
-}
-
-}  // namespace IPC