Use WaitableEvents to wake up sync IPC waiting

ipc/ipc_sync_message.h

 // Copyright (c) 2012 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 IPC_IPC_SYNC_MESSAGE_H_
 #define IPC_IPC_SYNC_MESSAGE_H_
 
 #include <stdint.h>
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
 #include <memory>
 #include <string>
 
 #include "build/build_config.h"
 #include "ipc/ipc_message.h"
 
+namespace base {
+class WaitableEvent;
+}
+
 namespace IPC {
 
 class MessageReplyDeserializer;
-class MojoEvent;
 
 class IPC_EXPORT SyncMessage : public Message {
  public:
   SyncMessage(int32_t routing_id,
               uint32_t type,
               PriorityValue priority,
               MessageReplyDeserializer* deserializer);
   ~SyncMessage() override;
 
   // Call this to get a deserializer for the output parameters.
@@ skipping 49 matching lines @@
  private:
   // Derived classes need to implement this, using the given iterator (which
   // is skipped past the header for synchronous messages).
   virtual bool SerializeOutputParameters(const Message& msg,
                                          base::PickleIterator iter) = 0;
 };
 
 // When sending a synchronous message, this structure contains an object
 // that knows how to deserialize the response.
 struct PendingSyncMsg {
-  PendingSyncMsg(int id, MessageReplyDeserializer* d, MojoEvent* e)
-      : id(id), deserializer(d), done_event(e), send_result(false) { }
+  PendingSyncMsg(int id, MessageReplyDeserializer* d, base::WaitableEvent* e)
+      : id(id), deserializer(d), done_event(e), send_result(false) {}
 
   int id;
   MessageReplyDeserializer* deserializer;
-  MojoEvent* done_event;
+  base::WaitableEvent* done_event;
   bool send_result;
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_MESSAGE_H_