Estimate a (close) upper bound on the size of black-marked objects on each page.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 8842a1b2daf89864d6912d992ff847ae47b941ec..9ee9799bb9e70666d4340e6031101843e93b3be0 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -836,6 +836,9 @@ bool String::MakeExternal(v8::String::ExternalStringResource* resource) {
   // Fill the remainder of the string with dead wood.
   int new_size = this->Size();  // Byte size of the external String object.
   heap->CreateFillerObjectAt(this->address() + new_size, size - new_size);
+  if (Marking::IsBlack(Marking::MarkBitFrom(this))) {
+    MemoryChunk::IncrementLiveBytes(this->address(), new_size - size);
+  }
   return true;
 }
 
@@ -882,6 +885,10 @@ bool String::MakeExternal(v8::String::ExternalAsciiStringResource* resource) {
   // Fill the remainder of the string with dead wood.
   int new_size = this->Size();  // Byte size of the external String object.
   heap->CreateFillerObjectAt(this->address() + new_size, size - new_size);
+  if (Marking::IsBlack(Marking::MarkBitFrom(this))) {
+    MemoryChunk::IncrementLiveBytes(this->address(), new_size - size);
+  }
+
   return true;
 }
 
@@ -2688,6 +2695,10 @@ MaybeObject* JSObject::NormalizeProperties(PropertyNormalizationMode mode,
   ASSERT(instance_size_delta >= 0);
   current_heap->CreateFillerObjectAt(this->address() + new_instance_size,
                                      instance_size_delta);
+  if (Marking::IsBlack(Marking::MarkBitFrom(this))) {
+    MemoryChunk::IncrementLiveBytes(this->address(), -instance_size_delta);
+  }
+
 
   set_map(new_map);
   new_map->clear_instance_descriptors();