Enter and Exit scope when calling into the native library tag handler

runtime/vm/bootstrap.cc

Index: runtime/vm/bootstrap.cc
===================================================================
--- runtime/vm/bootstrap.cc	(revision 32333)
+++ runtime/vm/bootstrap.cc	(working copy)
@@ -256,9 +256,7 @@
   // library tag handler so that we can load all the bootstrap libraries.
   isolate->set_library_tag_handler(BootstrapLibraryTagHandler);
 
-  // Enter the Dart Scope as we will be calling back into the library
-  // tag handler when compiling the bootstrap libraries.
-  Dart_EnterScope();
+  HANDLESCOPE(isolate);
 
   // Create library objects for all the bootstrap libraries.
   for (intptr_t i = 0;
@@ -309,9 +307,6 @@
     SetupNativeResolver();
   }
 
-  // Exit the Dart scope.
-  Dart_ExitScope();
-
   // Restore the library tag handler for the isolate.
   isolate->set_library_tag_handler(saved_tag_handler);