Fix issue 2888.

include/dart_api.h

 // 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.
 
 #ifndef INCLUDE_DART_API_H_
 #define INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
  *
  * Dart is a class-based programming language for creating structured
@@ skipping 1898 matching lines @@
   kCanonicalizeUrl
 } Dart_LibraryTag;
 
 // TODO(turnidge): Document.
 typedef Dart_Handle (*Dart_LibraryTagHandler)(Dart_LibraryTag tag,
                                               Dart_Handle library,
                                               Dart_Handle url,
                                               Dart_Handle import_map);
 
 /**
+ * Set library tag handler for the current isolate. This handler is used to
+ * handle the various tags encountered while loading libraries or scripts in
+ * the isolate.
+ *
+ * \param handler Handler code to be used for handling the various tags
+ *   encountered while loading libraries or scripts in the isolate.
+ *
+ * \return If no error occurs, the handler is set for the isolate.
+ *   Otherwise an error handle is returned.
+ *
+ * TODO(turnidge): Document.
+ */
+DART_EXPORT Dart_Handle Dart_SetLibraryTagHandler(
+    Dart_LibraryTagHandler handler);
+
+/**
  * Loads the root script for the current isolate.
  *
  * TODO(turnidge): Document.
  */
 DART_EXPORT Dart_Handle Dart_LoadScript(Dart_Handle url,
                                         Dart_Handle source,
-                                        Dart_LibraryTagHandler handler,
                                         Dart_Handle import_map);
 
 /**
  * Loads the root script for current isolate from a snapshot.
  *
  * \param buffer A buffer which contains a snapshot of the script.
  *
  * \return If no error occurs, the Library object corresponding to the root
  *   script is returned. Otherwise an error handle is returned.
  **/
@@ skipping 56 matching lines @@
 
 // --- Profiling support ----
 
 // External pprof support for gathering and dumping symbolic
 // information that can be used for better profile reports for
 // dynamically generated code.
 DART_EXPORT void Dart_InitPprofSupport();
 DART_EXPORT void Dart_GetPprofSymbolInfo(void** buffer, int* buffer_size);
 
 #endif  // INCLUDE_DART_API_H_