Reset progress bar of object to 0 when RecordWrites changes object color to grey.

BUG=v8:2423

Review URL: https://codereview.chromium.org/11308177

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13040 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/incremental-marking-inl.h

@@ -90,6 +90,10 @@ void IncrementalMarking::RecordWrites(HeapObject* obj) {
   if (IsMarking()) {
     MarkBit obj_bit = Marking::MarkBitFrom(obj);
     if (Marking::IsBlack(obj_bit)) {
+      MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
+      if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
+        chunk->set_progress_bar(0);
+      }
       BlackToGreyAndUnshift(obj, obj_bit);
       RestartIfNotMarking();
     }