Add v8::HeapGraphNode::GetHeapValue method.

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 814e9b3e9d578a62850a3dab5d46d41bdd022bf2..c075c031e1ddfbfbdbadf743b76948c3b380902f 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -1015,6 +1015,11 @@ int HeapEntry::RetainedSize(bool exact) {
 }
 
 
+Handle<HeapObject> HeapEntry::GetHeapObject() {
+  return snapshot_->collection()->FindHeapObjectById(id());
+}
+
+
 template<class Visitor>
 void HeapEntry::ApplyAndPaintAllReachable(Visitor* visitor) {
   List<HeapEntry*> list(10);
@@ -1375,8 +1380,8 @@ HeapObjectsMap::~HeapObjectsMap() {
 
 
 void HeapObjectsMap::SnapshotGenerationFinished() {
-    initial_fill_mode_ = false;
-    RemoveDeadEntries();
+  initial_fill_mode_ = false;
+  RemoveDeadEntries();
 }
 
 
@@ -1522,6 +1527,26 @@ void HeapSnapshotsCollection::RemoveSnapshot(HeapSnapshot* snapshot) {
 }
 
 
+Handle<HeapObject> HeapSnapshotsCollection::FindHeapObjectById(uint64_t id) {
+  // First perform a full GC in order to avoid dead objects.
+  HEAP->CollectAllGarbage(Heap::kMakeHeapIterableMask);
+  AssertNoAllocation no_allocation;
+  HeapObject* object = NULL;
+  HeapIterator iterator(HeapIterator::kFilterUnreachable);
+  // Make sure that object with the given id is still reachable.
+  for (HeapObject* obj = iterator.next();
+       obj != NULL;
+       obj = iterator.next()) {
+    if (ids_.FindObject(obj->address()) == id) {

[Vyacheslav Egorov (Chromium), 2011/09/26 14:22:10]

this is not going to work if obj was in new space or was on the page that was
compacted.

we either will fail to find the object or will return the wrong one.

[mnaganov (inactive), 2011/09/26 14:28:19]

What do you mean? We start keeping IDs for heap objects after the first heap
snapshot has been done. We should have 'HeapProfiler::ObjectMoveEvent' in proper
places to track existing object moves, and new objects are added when we are
taking the next snapshot.

+      ASSERT(object == NULL);
+      object = obj;
+      // Can't break -- kFilterUnreachable requires full heap traversal.

[Vyacheslav Egorov (Chromium), 2011/09/26 14:22:10]

We can fix this by switching kFilterUnreachable from intrusive marking to
mark-bits based marking (just saying).

[mnaganov (inactive), 2011/09/26 14:28:19]

Yes, that's a good idea. I will create a bug to track this.

+    }
+  }
+  return object != NULL ? Handle<HeapObject>(object) : Handle<HeapObject>();
+}
+
+
 HeapEntry *const HeapEntriesMap::kHeapEntryPlaceholder =
     reinterpret_cast<HeapEntry*>(1);