[mojo] Use a pipe path to initialise Mojo in elevated utility processes.

mojo/edk/embedder/platform_handle.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_EMBEDDER_PLATFORM_HANDLE_H_
 #define MOJO_EDK_EMBEDDER_PLATFORM_HANDLE_H_
 
 #include "build/build_config.h"
 #include "mojo/edk/system/system_impl_export.h"
 
@@ skipping 54 matching lines @@
 
   void CloseIfNecessary();
 
   bool is_valid() const { return handle != INVALID_HANDLE_VALUE; }
 
   HANDLE handle;
 
   // A Windows HANDLE may be duplicated to another process but not yet sent to
   // that process. This tracks the handle's owning process.
   base::ProcessHandle owning_process;
+
+  // A Windows HANDLE may be an unconnected named pipe. In this case, we need to
+  // wait for a connection before communicating on the pipe.
+  bool needs_connection = false;
 };
 #else
 #error "Platform not yet supported."
 #endif
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_EMBEDDER_PLATFORM_HANDLE_H_