Replace the gc extension in content shell with a gin::Wrappable class

content/shell/renderer/gc_extension.cc

-// Copyright 2013 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 "content/shell/renderer/gc_extension.h"
-
-#include "v8/include/v8.h"
-
-const char kGCExtensionName[] = "v8/GCController";
-
-namespace extensions_v8 {
-
-// static
-v8::Extension* GCExtension::Get() {
-  v8::Extension* extension = new v8::Extension(
-      kGCExtensionName,
-      "(function () {"
-      "   var v8_gc;"
-      "   if (gc) v8_gc = gc;"
-      "   GCController = new Object();"
-      "   GCController.collect ="
-      "     function() {if (v8_gc) v8_gc(); };"
-      "   GCController.minorCollect ="
-      "     function() {if (v8_gc) v8_gc(true); };"
-      " })();");
-  return extension;
-}
-
-}  // namespace extensions_v8