Change type of Dart_PersistentHandle to be the same as Dart_Handle so that

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 167 matching lines @@
  *
  * Local handles are allocated within the current scope (see
  * Dart_EnterScope) and go away when the current scope exits. Unless
  * otherwise indicated, callers should assume that all functions in
  * the Dart embedding api return local handles.
  *
  * Persistent handles are allocated within the current isolate. They
  * can be used to store objects across scopes. Persistent handles have
  * the lifetime of the current isolate unless they are explicitly
  * deallocated (see Dart_DeletePersistentHandle).
+ * The type Dart_Handle represents a handle (both local and persistent).
+ * The type Dart_PersistentHandle is a Dart_Handle and it is used to
+ * document that a persistent handle is expected as a parameter to a call
+ * or the return value from a call is a persistent handle.
  */
 typedef struct _Dart_Handle* Dart_Handle;
-typedef struct _Dart_PersistentHandle* Dart_PersistentHandle;
+typedef Dart_Handle Dart_PersistentHandle;
 typedef struct _Dart_WeakPersistentHandle* Dart_WeakPersistentHandle;
 
 typedef void (*Dart_WeakPersistentHandleFinalizer)(
     Dart_WeakPersistentHandle handle,
     void* peer);
 typedef void (*Dart_PeerFinalizer)(void* peer);
 
 /**
  * Is this an error handle?
  *
@@ skipping 2071 matching lines @@
  *
  * \param object An object.
  * \param peer A value to store in the peer field.
  *
  * \return Returns an error if 'object' is a subtype of Null, num, or
  *   bool.
  */
 DART_EXPORT Dart_Handle Dart_SetPeer(Dart_Handle object, void* peer);
 
 #endif  /* INCLUDE_DART_API_H_ */  /* NOLINT */