Fix issue 2888.

vm/dart_api_impl.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 "include/dart_api.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/dart.h"
@@ skipping 2946 matching lines @@
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
   Isolate* isolate = arguments->isolate();
   DARTSCOPE(isolate);
   arguments->SetReturn(Object::Handle(isolate, Api::UnwrapHandle(retval)));
 }
 
 
 // --- Scripts and Libraries ---
 
 
+DART_EXPORT Dart_Handle Dart_SetLibraryTagHandler(
+    Dart_LibraryTagHandler handler) {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  isolate->set_library_tag_handler(handler);
+  return Api::Success(isolate);
+}
+
+
 // NOTE: Need to pass 'result' as a parameter here in order to avoid
 // warning: variable 'result' might be clobbered by 'longjmp' or 'vfork'
 // which shows up because of the use of setjmp.
 static void CompileSource(Isolate* isolate,
                           const Library& lib,
                           const String& url,
                           const String& source,
                           RawScript::Kind kind,
                           Dart_Handle* result) {
   bool update_lib_status = (kind == RawScript::kScript ||
@@ skipping 14 matching lines @@
     *result = Api::NewHandle(isolate, error.raw());
     if (update_lib_status) {
       lib.SetLoadError();
     }
   }
 }
 
 
 DART_EXPORT Dart_Handle Dart_LoadScript(Dart_Handle url,
                                         Dart_Handle source,
-                                        Dart_LibraryTagHandler handler,
                                         Dart_Handle import_map) {
   TIMERSCOPE(time_script_loading);
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   const String& url_str = Api::UnwrapStringHandle(isolate, url);
   if (url_str.IsNull()) {
     RETURN_TYPE_ERROR(isolate, url, String);
   }
   const String& source_str = Api::UnwrapStringHandle(isolate, source);
   if (source_str.IsNull()) {
     RETURN_TYPE_ERROR(isolate, source, String);
   }
   const Array& mapping_array = Api::UnwrapArrayHandle(isolate, import_map);
   Library& library =
       Library::Handle(isolate, isolate->object_store()->root_library());
   if (!library.IsNull()) {
     const String& library_url = String::Handle(isolate, library.url());
     return Api::NewError("%s: A script has already been loaded from '%s'.",
                          CURRENT_FUNC, library_url.ToCString());
   }
-  isolate->set_library_tag_handler(handler);
   library = Library::New(url_str);
   if (mapping_array.IsNull()) {
     library.set_import_map(Array::Handle(isolate, Array::Empty()));
   } else {
     library.set_import_map(mapping_array);
   }
   library.Register();
   isolate->object_store()->set_root_library(library);
   Dart_Handle result;
   CompileSource(isolate,
@@ skipping 259 matching lines @@
       *buffer = NULL;
     }
     delete debug_region;
   } else {
     *buffer = NULL;
     *buffer_size = 0;
   }
 }
 
 }  // namespace dart