Remove the ability to allow multiple gc prologue and gc epilogue callbacks

runtime/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
@@ skipping 588 matching lines @@
  * \param callback A function pointer to an epilogue callback
  *   function.  This function must have been added as an epilogue
  *   callback.
  *
  * \return Success if the callback was removed.  Otherwise, returns an
  *   error handle.
  */
 DART_EXPORT Dart_Handle Dart_RemoveGcEpilogueCallback(
     Dart_GcEpilogueCallback callback);
 
+/**
+ * Adds garbage collection callbacks (prologue and epilogue).
+ *
+ * \param prologue_callback A function pointer to a prologue callback function.
+ *   A prologue callback function should not be already set when this function
+ *   is called. A NULL value removes the existing prologue callback function
+ *   if any.
+ *
+ * \param epilogue_callback A function pointer to an epilogue callback function.
+ *   An epilogue callback function should not be already set when this function
+ *   is called. A NULL value removes the existing epilogue callback function
+ *   if any.
+ *
+ * \return Success if the callbacks were added.  Otherwise, returns an
+ *   error handle.
+ */
+DART_EXPORT Dart_Handle Dart_SetGcCallbacks(
+    Dart_GcPrologueCallback prologue_callback,
+    Dart_GcEpilogueCallback epilogue_callback);
 
 /*
  * ==========================
  * Initialization and Globals
  * ==========================
  */
 
 /**
  * Gets the version string for the Dart VM.
  *
@@ skipping 1932 matching lines @@
  * NOTE: If multiple callbacks with the same name are registered, only the
  * last callback registered will be remembered.
  */
 DART_EXPORT void Dart_RegisterRootServiceRequestCallback(
     const char* name,
     Dart_ServiceRequestCallback callback,
     void* user_data);
 
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */