Tweaks to PPB_VarArrayBuffer in preperation for taking out of Dev.

ppapi/proxy/plugin_array_buffer_var.cc

 // Copyright (c) 2011 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 "ppapi/proxy/plugin_array_buffer_var.h"
 
 #include <stdlib.h>
 
 #include <limits>
 
 namespace ppapi {
 
 PluginArrayBufferVar::PluginArrayBufferVar(uint32 size_in_bytes)
     : buffer_(size_in_bytes) {
 }
 
 PluginArrayBufferVar::~PluginArrayBufferVar() {
 }
 
 void* PluginArrayBufferVar::Map() {
   if (buffer_.empty())
     return NULL;
   return &(buffer_[0]);
 }
 
+void PluginArrayBufferVar::Unmap() {
+  // We don't actually use shared memory yet, so do nothing.
+}
+
 uint32 PluginArrayBufferVar::ByteLength() {
   return buffer_.size();
 }
 
 }  // namespace ppapi