Turn libplatform into a component

src/libplatform/default-platform.h

Index: src/libplatform/default-platform.h
diff --git a/src/libplatform/default-platform.h b/src/libplatform/default-platform.h
index 0fd7e5ad890a3090ab794c9d5c734a6ea29f45f3..99c7b0502bb7bf2cefb54e9eaebf7014800d3cac 100644
--- a/src/libplatform/default-platform.h
+++ b/src/libplatform/default-platform.h
@@ -10,8 +10,10 @@
 #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"
@@ -27,7 +29,7 @@ namespace tracing {
 class TracingController;
 }
 
-class DefaultPlatform : public Platform {
+class V8_PLATFORM_EXPORT DefaultPlatform : public NON_EXPORTED_BASE(Platform) {
  public:
   DefaultPlatform();
   virtual ~DefaultPlatform();