Make all allocation of external arrays used for IO use the IOBuffer class

runtime/bin/io_buffer.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef IO_BUFFER_H_
 #define IO_BUFFER_H_
 
 #include "platform/globals.h"
 
 #include "include/dart_api.h"
 
 class IOBuffer {
  public:
+  // Allocate an IO buffer dart object (of type Uint8List) backed by
+  // an external byte array.
   static Dart_Handle Allocate(intptr_t size, uint8_t **buffer);
 
+  // Allocate IO buffer storage.
+  static uint8_t* Allocate(intptr_t size);
+
+  // Function for disposing of IO buffer storage. All backing storage
+  // for IO buffers must be freed using this function.
+  static void Free(void* buffer) {
+    delete[] reinterpret_cast<uint8_t*>(buffer);
+  }
+
  private:
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(IOBuffer);
 };
 
 #endif  // IO_BUFFER_H_