Always leak the Mojo parent pipe handle on child process shutdown.

mojo/edk/system/channel_posix.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 <errno.h>
 #include <sys/socket.h>
 
 #include <algorithm>
@@ skipping 119 matching lines @@
       }
     }
     if (write_error) {
       // Do not synchronously invoke OnError(). Write() may have been called by
       // the delegate and we don't want to re-enter it.
       io_task_runner_->PostTask(FROM_HERE,
                                 base::Bind(&ChannelPosix::OnError, this));
     }
   }
 
+  void LeakHandle() override {
+    DCHECK(io_task_runner_->RunsTasksOnCurrentThread());
+    leak_handle_ = true;
+  }
+
   bool GetReadPlatformHandles(
       size_t num_handles,
       const void* extra_header,
       size_t extra_header_size,
       ScopedPlatformHandleVectorPtr* handles) override {
     if (num_handles > std::numeric_limits<uint16_t>::max())
       return false;
 #if defined(OS_MACOSX) && !defined(OS_IOS)
     // On OSX, we can have mach ports which are located in the extra header
     // section.
@@ skipping 82 matching lines @@
       io_task_runner_->PostTask(
           FROM_HERE, base::Bind(&ChannelPosix::WaitForWriteOnIOThread, this));
     }
   }
 
   void ShutDownOnIOThread() {
     base::MessageLoop::current()->RemoveDestructionObserver(this);
 
     read_watcher_.reset();
     write_watcher_.reset();
+    if (leak_handle_)
+      ignore_result(handle_.release());
     handle_.reset();
 #if defined(OS_MACOSX)
     handles_to_close_.reset();
 #endif
 
     // May destroy the |this| if it was the last reference.
     self_ = nullptr;
   }
 
   // base::MessageLoop::DestructionObserver:
@@ skipping 230 matching lines @@
   std::unique_ptr<base::MessageLoopForIO::FileDescriptorWatcher> write_watcher_;
 
   std::deque<PlatformHandle> incoming_platform_handles_;
 
   // Protects |pending_write_| and |outgoing_messages_|.
   base::Lock write_lock_;
   bool pending_write_ = false;
   bool reject_writes_ = false;
   std::deque<MessageView> outgoing_messages_;
 
+  bool leak_handle_ = false;
+
 #if defined(OS_MACOSX)
   base::Lock handles_to_close_lock_;
   ScopedPlatformHandleVectorPtr handles_to_close_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ChannelPosix);
 };
 
 }  // namespace
 
 // static
 scoped_refptr<Channel> Channel::Create(
     Delegate* delegate,
     ScopedPlatformHandle platform_handle,
     scoped_refptr<base::TaskRunner> io_task_runner) {
   return new ChannelPosix(delegate, std::move(platform_handle), io_task_runner);
 }
 
 }  // namespace edk
 }  // namespace mojo