Move JSSyntaxRegExp to core as a private member. This removes the last refrences to dart:coreimpl.

runtime/vm/bootstrap_natives.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap.h"
 
 #include "include/dart_api.h"
 
 #include "vm/bootstrap_natives.h"
 #include "vm/dart_api_impl.h"
@@ skipping 42 matching lines @@
 void Bootstrap::SetupNativeResolver() {
   Library& library = Library::Handle();
 
   Dart_NativeEntryResolver resolver =
       reinterpret_cast<Dart_NativeEntryResolver>(BootstrapNatives::Lookup);
 
   library = Library::CoreLibrary();
   ASSERT(!library.IsNull());
   library.set_native_entry_resolver(resolver);
 
-  library = Library::CoreImplLibrary();
-  ASSERT(!library.IsNull());
-  library.set_native_entry_resolver(resolver);
-
   library = Library::CollectionLibrary();
   ASSERT(!library.IsNull());
   library.set_native_entry_resolver(resolver);
 
   library = Library::MirrorsLibrary();
   ASSERT(!library.IsNull());
   library.set_native_entry_resolver(resolver);
 
   library = Library::IsolateLibrary();
   ASSERT(!library.IsNull());
   library.set_native_entry_resolver(resolver);
 
   library = Library::ScalarlistLibrary();
   ASSERT(!library.IsNull());
   library.set_native_entry_resolver(resolver);
 }
 
 }  // namespace dart