Ensure black and gray objects are kept around by scavenger

src/heap/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 
 #include "src/allocation.h"
@@ skipping 2843 matching lines @@
   // same page, so FromSpaceStart() might be above FromSpaceEnd().
   Address FromSpacePageLow() { return from_space_.page_low(); }
   Address FromSpacePageHigh() { return from_space_.page_high(); }
   Address FromSpaceStart() { return from_space_.space_start(); }
   Address FromSpaceEnd() { return from_space_.space_end(); }
 
   // Get the extent of the active semispace's pages' memory.
   Address ToSpaceStart() { return to_space_.space_start(); }
   Address ToSpaceEnd() { return to_space_.space_end(); }
 
+  SemiSpace* from_space() { return &from_space_; }
+
   inline bool ToSpaceContainsSlow(Address a);
   inline bool FromSpaceContainsSlow(Address a);
   inline bool ToSpaceContains(Object* o);
   inline bool FromSpaceContains(Object* o);
 
   // Try to switch the active semispace to a new, empty, page.
   // Returns false if this isn't possible or reasonable (i.e., there
   // are no pages, or the current page is already empty), or true
   // if successful.
   bool AddFreshPage();
@@ skipping 323 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_