Lazy peer API.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
diff --git a/runtime/vm/pages.cc b/runtime/vm/pages.cc
index 5168ff5d494fc000e2768c00d2ef920465c38efa..e50515a274c9b7b2beefec0229895dea6f9c7e7d 100644
--- a/runtime/vm/pages.cc
+++ b/runtime/vm/pages.cc
@@ -308,6 +308,26 @@ void PageSpace::VisitObjects(ObjectVisitor* visitor) const {
 }
 
 
+void PageSpace::SetPeer(RawObject* raw_obj, void* peer) {
+  if (peer == NULL) {
+    peer_.erase(raw_obj);
+  } else {
+    peer_[raw_obj] = peer;
+  }
+}
+
+
+void* PageSpace::GetPeer(RawObject* raw_obj) {
+  std::map<RawObject*, void*>::iterator it = peer_.find(raw_obj);
+  return (it == peer_.end()) ? NULL : it->second;
+}
+
+
+int64_t PageSpace::PeerCount() const {
+  return static_cast<int64_t>(peer_.size());
+}
+
+
 void PageSpace::VisitObjectPointers(ObjectPointerVisitor* visitor) const {
   HeapPage* page = pages_;
   while (page != NULL) {
@@ -385,7 +405,7 @@ void PageSpace::MarkSweep(bool invoke_api_callbacks, const char* gc_reason) {
   int64_t start = OS::GetCurrentTimeMillis();
 
   // Mark all reachable old-gen objects.
-  GCMarker marker(heap_);
+  GCMarker marker(heap_, &peer_);
   marker.MarkObjects(isolate, this, invoke_api_callbacks);
 
   // Reset the bump allocation page to unused.