Turn libplatform into a component

src/libplatform/default-platform.h

 // 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.
 
 #ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 #define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
 #include <functional>
 #include <map>
 #include <queue>
 #include <vector>
 
+#include "include/libplatform/libplatform-export.h"
 #include "include/libplatform/v8-tracing.h"
 #include "include/v8-platform.h"
+#include "src/base/compiler-specific.h"
 #include "src/base/macros.h"
 #include "src/base/platform/mutex.h"
 #include "src/libplatform/task-queue.h"
 
 namespace v8 {
 namespace platform {
 
 class TaskQueue;
 class Thread;
 class WorkerThread;
 
 namespace tracing {
 class TracingController;
 }
 
-class DefaultPlatform : public Platform {
+class V8_PLATFORM_EXPORT DefaultPlatform : public NON_EXPORTED_BASE(Platform) {
  public:
   DefaultPlatform();
   virtual ~DefaultPlatform();
 
   void SetThreadPoolSize(int thread_pool_size);
 
   void EnsureInitialized();
 
   bool PumpMessageLoop(v8::Isolate* isolate);
 
@@ skipping 42 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatform);
 };
 
 
 }  // namespace platform
 }  // namespace v8
 
 
 #endif  // V8_LIBPLATFORM_DEFAULT_PLATFORM_H_