Revert of Making the Mojo Channel Messages legacy mode dynamic.

mojo/edk/system/channel.h

 // 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.
 
 #ifndef MOJO_EDK_SYSTEM_CHANNEL_H_
 #define MOJO_EDK_SYSTEM_CHANNEL_H_
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 153 matching lines @@
     // Prepares the handles in this message for use in a different process.
     // Upon calling this the handles should belong to |from_process|; after the
     // call they'll belong to |to_process|. The source handles are always
     // closed by this call. Returns false iff one or more handles failed
     // duplication.
     static bool RewriteHandles(base::ProcessHandle from_process,
                                base::ProcessHandle to_process,
                                PlatformHandleVector* handles);
 #endif
 
-    static void SetUseLegacyTransportProtocol(bool use_legacy_protocol);
+    void SetVersionForTest(uint16_t version_number);
 
    private:
     size_t size_ = 0;
     size_t max_handles_ = 0;
     char* data_ = nullptr;
 
     ScopedPlatformHandleVectorPtr handle_vector_;
 
 #if defined(OS_WIN)
     // On Windows, handles are serialised into the extra header section.
@@ skipping 109 matching lines @@
   Delegate* delegate_;
   const std::unique_ptr<ReadBuffer> read_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(Channel);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_CHANNEL_H_