Move platform abstraction to base library

src/extensions/free-buffer-extension.cc

 // Copyright 2013 the V8 project 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 "src/extensions/free-buffer-extension.h"
-#include "src/platform.h"
+
+#include "src/base/platform/platform.h"
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
 
 v8::Handle<v8::FunctionTemplate> FreeBufferExtension::GetNativeFunctionTemplate(
     v8::Isolate* isolate,
     v8::Handle<v8::String> str) {
   return v8::FunctionTemplate::New(isolate, FreeBufferExtension::FreeBuffer);
 }
 
 
 void FreeBufferExtension::FreeBuffer(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   v8::Handle<v8::ArrayBuffer> arrayBuffer = args[0].As<v8::ArrayBuffer>();
   v8::ArrayBuffer::Contents contents = arrayBuffer->Externalize();
   V8::ArrayBufferAllocator()->Free(contents.Data(), contents.ByteLength());
 }
 
 } }  // namespace v8::internal