Reduce LiveBytes assert to one that only triggers if the miscalculation is

src/spaces.cc

 // 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 821 matching lines @@
       // All the interior pointers should be contained in the heap.
       int size = object->Size();
       object->IterateBody(map->instance_type(), size, visitor);
       if (Marking::IsBlack(Marking::MarkBitFrom(object))) {
         black_size += size;
       }
 
       ASSERT(object->address() + size <= top);
       end_of_previous_object = object->address() + size;
     }
-    ASSERT_LE(black_size, page->LiveBytes());
+    // TODO(1672): Remove the non-zero part of this.
+    ASSERT(page->LiveBytes() != 0 || black_size <= page->LiveBytes());
   }
   ASSERT(allocation_pointer_found_in_space);
 }
 #endif
 
 
 // -----------------------------------------------------------------------------
 // NewSpace implementation
 
 
@@ skipping 1665 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal