New GC related APIs: Implicit references.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 38312e9b1fffbe1fd1171122cd5a87789c3cd905..b40a4bf92dd66ae5f072fc7fe9e2eaafd83eded4 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -3555,17 +3555,39 @@ class V8EXPORT V8 {
                                     RetainedObjectInfo* info);
 
   /**
+   * Sets a representative object to a group. Used in conjunction with implicit
+   * references: If you're going to use AddImplicitReference with the group, you
+   * need to set a representative object too.
+   */
+  static void SetObjectGroupRepresentative(Isolate* isolate,
+                                           UniqueId id,
+                                           const Persistent<Object>& object);
+
+  /**
    * Allows the host application to declare implicit references between
    * the objects: if |parent| is alive, all |children| are alive too.
    * After each garbage collection, all implicit references
    * are removed.  It is intended to be used in the before-garbage-collection
    * callback function.
    */
+  // TODO(marja): Deprecate AddImplicitReferences. Use
+  // SetObjectGroupRepresentativeObject and AddImplicitReference instead.
   static void AddImplicitReferences(Persistent<Object> parent,
                                     Persistent<Value>* children,
                                     size_t length);
 
   /**
+   * Allows the host application to declare implicit references. If the
+   * representative object of the object group (identified by id) is alive, the
+   * children are alive too. After each garbage collection, all implicit
+   * references are removed. It is intended to be used in the
+   * before-garbage-collection callback function.
+   */
+  static void AddImplicitReference(Isolate* isolate,
+                                   UniqueId id,
+                                   const Persistent<Value>& object);
+
+  /**
    * Initializes from snapshot if possible. Otherwise, attempts to
    * initialize from scratch.  This function is called implicitly if
    * you use the API without calling it first.