Implement weak references sets and provide an embedding API.

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
  *
  * Dart is a class-based programming language for creating structured
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     void* peer,
     Dart_WeakPersistentHandleFinalizer callback);
 
 /**
  * Is this object a weak persistent handle?
  *
  * Requires there to be a current isolate.
  */
 DART_EXPORT bool Dart_IsWeakPersistentHandle(Dart_Handle object);
 
+
+/**
+ * Constructs a set of weak references from the Cartesian product of
+ * the objects in the key set and the objects in values set.
+ *
+ * \param keys A set of object references.  These references will be
+ *   considered weak by the garbage collector.
+ * \param num_keys the number of objects in the keys set.
+ * \param values A set of object references.  These references will be
+ *   considered weak by garbage collector unless any object reference
+ *   in 'keys' is found to be strong.
+ * \param num_values the size of the values set
+ *
+ * \return Success if the weak reference set could be created.
+ *   Otherwise, returns an error handle.
+ */
+DART_EXPORT Dart_Handle Dart_NewWeakReferenceSet(Dart_Handle* keys,
+                                                 intptr_t num_keys,
+                                                 Dart_Handle* values,
+                                                 intptr_t num_values);
+
+
 // --- Initialization and Globals ---
 
 /**
  * An isolate creation and initialization callback function.
  *
  * This callback, provided by the embedder, is called when an isolate needs
  * to be created. The callback should create an isolate and load the
  * required scripts for execution.
  *
  * \param error A structure into which the embedder can place a
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 // --- 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_