Provide a convenience array buffer allocator

samples/hello-world.cc

 // Copyright 2015 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 <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "include/libplatform/libplatform.h"
 #include "include/v8.h"
 
 using namespace v8;
 
-class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
- public:
-  virtual void* Allocate(size_t length) {
-    void* data = AllocateUninitialized(length);
-    return data == NULL ? data : memset(data, 0, length);
-  }
-  virtual void* AllocateUninitialized(size_t length) { return malloc(length); }
-  virtual void Free(void* data, size_t) { free(data); }
-};
-
-
 int main(int argc, char* argv[]) {
   // Initialize V8.
   V8::InitializeICUDefaultLocation(argv[0]);
   V8::InitializeExternalStartupData(argv[0]);
   Platform* platform = platform::CreateDefaultPlatform();
   V8::InitializePlatform(platform);
   V8::Initialize();
 
   // Create a new Isolate and make it the current one.
-  ArrayBufferAllocator allocator;
   Isolate::CreateParams create_params;
-  create_params.array_buffer_allocator = &allocator;
+  create_params.array_buffer_allocator =
+      v8::ArrayBuffer::Allocator::NewDefaultAllocator();
   Isolate* isolate = Isolate::New(create_params);
   {
     Isolate::Scope isolate_scope(isolate);
 
     // Create a stack-allocated handle scope.
     HandleScope handle_scope(isolate);
 
     // Create a new context.
     Local<Context> context = Context::New(isolate);
 
@@ skipping 14 matching lines @@
     // Convert the result to an UTF8 string and print it.
     String::Utf8Value utf8(result);
     printf("%s\n", *utf8);
   }
 
   // Dispose the isolate and tear down V8.
   isolate->Dispose();
   V8::Dispose();
   V8::ShutdownPlatform();
   delete platform;
+  delete create_params.array_buffer_allocator;
   return 0;
 }