Remove handler from MessagePumpForIO::IOContext.

mojo/edk/system/channel_win.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 "mojo/edk/system/channel.h"
 
 #include <stdint.h>
 #include <windows.h>
 
 #include <algorithm>
@@ skipping 62 matching lines @@
  public:
   ChannelWin(Delegate* delegate,
              ScopedPlatformHandle handle,
              scoped_refptr<base::TaskRunner> io_task_runner)
       : Channel(delegate),
         self_(this),
         handle_(std::move(handle)),
         io_task_runner_(io_task_runner) {
     sentinel_ = ~reinterpret_cast<uintptr_t>(this);
     CHECK(handle_.is_valid());
-    memset(&read_context_, 0, sizeof(read_context_));
-    read_context_.handler = this;
-
-    memset(&write_context_, 0, sizeof(write_context_));
-    write_context_.handler = this;
   }
 
   void Start() override {
     io_task_runner_->PostTask(
         FROM_HERE, base::Bind(&ChannelWin::StartOnIOThread, this));
   }
 
   void ShutDownImpl() override {
     // Always shut down asynchronously when called through the public interface.
     io_task_runner_->PostTask(
@@ skipping 219 matching lines @@
 // static
 scoped_refptr<Channel> Channel::Create(
     Delegate* delegate,
     ScopedPlatformHandle platform_handle,
     scoped_refptr<base::TaskRunner> io_task_runner) {
   return new ChannelWin(delegate, std::move(platform_handle), io_task_runner);
 }
 
 }  // namespace edk
 }  // namespace mojo