Ensure that in-flight message pipes are always closed and the other end is notified.

mojo/edk/system/message_in_transit.h

 // Copyright 2013 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 MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
 #define MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 28 matching lines @@
 // main buffer a multiple of |kMessageAlignment| bytes in size.
 //
 // See |TransportData| for a description of the (serialized) transport data
 // buffer.
 class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
  public:
   enum class Type : uint16_t {
     MESSAGE = 0,
     // Since there's a limit on how many fds can be sent in one sendmsg call, if
     // a message has more than that the fds are sent in this message type first.
-    RAW_CHANNEL_POSIX_EXTRA_PLATFORM_HANDLES = 1,
+    RAW_CHANNEL_POSIX_EXTRA_PLATFORM_HANDLES,
     // When a RawChannel is serialized, there could be pending messages to be
     // written to the pipe. They are serialized to shared memory. When they're
     // deserialized on the receiving end, we want to write them to the pipe
     // without any message headers, because those have already been written.
-    RAW_MESSAGE = 3,
+    RAW_MESSAGE,
+    // Tells the other side to close its pipe. This is needed because when a
+    // MessagePipeDispatcher is closed, it has to wait to flush any pending
+    // messages or else in-flight message pipes won't be closed.
+    QUIT_MESSAGE,
   };
 
   // Messages (the header and data) must always be aligned to a multiple of this
   // quantity (which must be a power of 2).
   static const size_t kMessageAlignment = 8;
 
   // Forward-declare |Header| so that |View| can use it:
  private:
   struct Header;
 
@@ skipping 171 matching lines @@
 MOJO_SYSTEM_IMPL_EXPORT inline std::ostream& operator<<(
     std::ostream& out,
     MessageInTransit::Type type) {
   return out << static_cast<uint16_t>(type);
 }
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_