Merged from GC branch to bleeding_edge

src/incremental-marking.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 120 matching lines @@
   void RecordWriteOfCodeEntry(JSFunction* host, Object** slot, Code* value);
 
   inline void RecordWrites(HeapObject* obj);
 
   inline void BlackToGreyAndUnshift(HeapObject* obj, MarkBit mark_bit);
 
   inline void WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit);
 
   inline void WhiteToGrey(HeapObject* obj, MarkBit mark_bit);
 
-  // Does white->black or grey->grey
+  // Does white->black or keeps gray or black color. Returns true if converting
+  // white to black.
   inline bool MarkBlackOrKeepGrey(MarkBit mark_bit) {
     ASSERT(!Marking::IsImpossible(mark_bit));
-    if (mark_bit.Get()) return false;
+    if (mark_bit.Get()) {
+      // Grey or black: Keep the color.
+      return false;
+    }
     mark_bit.Set();
-    ASSERT(!Marking::IsWhite(mark_bit));
-    ASSERT(!Marking::IsImpossible(mark_bit));
+    ASSERT(Marking::IsBlack(mark_bit));
     return true;
   }
 
   inline int steps_count() {
     return steps_count_;
   }
 
   inline double steps_took() {
     return steps_took_;
   }
@@ skipping 81 matching lines @@
   bool should_hurry_;
   int allocation_marking_factor_;
   intptr_t allocated_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_INCREMENTAL_MARKING_H_