Make sure we register extensions only once. Removed unused member variable.

src/bootstrapper.h

Index: src/bootstrapper.h
diff --git a/src/bootstrapper.h b/src/bootstrapper.h
index e33415eeb9ca5f9e5157f0bf23a8b93cff8af286..476ac12e1491e70431ad9059463ed13fa75c11c7 100644
--- a/src/bootstrapper.h
+++ b/src/bootstrapper.h
@@ -88,6 +88,8 @@ class SourceCodeCache BASE_EMBEDDED {
 // context.
 class Bootstrapper {
  public:
+  static void InitializeOncePerProcess();
+
   // Requires: Heap::SetUp has been called.
   void Initialize(bool create_heap_objects);
   void TearDown();