Remove Dart_VisitPrologueWeakHandles from the API header.

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 568 matching lines @@
  *   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);
 
-typedef void (*Dart_GcPrologueWeakHandleCallback)(void* isolate_callback_data,
-                                                  Dart_WeakPersistentHandle obj,
-                                                  intptr_t num_native_fields,
-                                                  intptr_t* native_fields);
-
-DART_EXPORT Dart_Handle Dart_VisitPrologueWeakHandles(
-    Dart_GcPrologueWeakHandleCallback callback);
 
 /*
  * ==========================
  * Initialization and Globals
  * ==========================
  */
 
 /**
  * Gets the version string for the Dart VM.
  *
@@ skipping 2578 matching lines @@
 /**
  *  Returns whether the VM was initialized with a precompiled snapshot. Only
  *  valid after Dart_Initialize.
  *  DEPRECATED. This is currently used to disable Platform.executable and
  *  Platform.resolvedExecutable under precompilation to prevent process
  *  spawning tests from becoming fork-bombs.
  */
 DART_EXPORT bool Dart_IsRunningPrecompiledCode();
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */