Implement weak persistent handles in the Dart API.

runtime/vm/isolate.cc

 // Copyright (c) 2011, 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.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 
 #include "vm/assert.h"
 #include "vm/bigint_store.h"
@@ skipping 316 matching lines @@
     }
   }
 
   // Indicates success.
   return Object::null();
 }
 
 
 void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
                                   bool validate_frames) {
+  VisitStrongObjectPointers(visitor, validate_frames);
+  VisitWeakObjectPointers(visitor);
+}
+
+
+void Isolate::VisitStrongObjectPointers(ObjectPointerVisitor* visitor,
+                                        bool validate_frames) {
   ASSERT(visitor != NULL);
 
   // Visit objects in the object store.
   object_store()->VisitObjectPointers(visitor);
 
   // Visit objects in per isolate stubs.
   StubCode::VisitObjectPointers(visitor);
 
   // Visit objects in zones.
   current_zone()->VisitObjectPointers(visitor);
 
   // Iterate over all the stack frames and visit objects on the stack.
   StackFrameIterator frames_iterator(validate_frames);
   StackFrame* frame = frames_iterator.NextFrame();
   while (frame != NULL) {
     frame->VisitObjectPointers(visitor);
     frame = frames_iterator.NextFrame();
   }
 
   // Visit the dart api state for all local and persistent handles.
   if (api_state() != NULL) {
-    api_state()->VisitObjectPointers(visitor);
+    api_state()->VisitStrongObjectPointers(visitor);
   }
 
   // Visit all objects in the code index table.
   if (code_index_table() != NULL) {
     code_index_table()->VisitObjectPointers(visitor);
   }
 
   // Visit the top context which is stored in the isolate.
   visitor->VisitPointer(reinterpret_cast<RawObject**>(&top_context_));
 
   // Visit objects in the debugger.
   debugger()->VisitObjectPointers(visitor);
 }
 
+
+void Isolate::VisitWeakObjectPointers(ObjectPointerVisitor* visitor) {
+  if (api_state() != NULL) {
+    api_state()->VisitWeakObjectPointers(visitor);
+  }
+}
+
 }  // namespace dart