Remove unmarked entries from per context map caches.

src/v8-counters.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 45 matching lines @@
 // this problem.  Please avoid using recursive macros of this length when
 // possible.
 #define STATS_COUNTER_LIST_1(SC)                                      \
   /* Global Handle Count*/                                            \
   SC(global_handles, V8.GlobalHandles)                                \
   /* Mallocs from PCRE */                                             \
   SC(pcre_mallocs, V8.PcreMallocCount)                                \
   /* OS Memory allocated */                                           \
   SC(memory_allocated, V8.OsMemoryAllocated)                          \
   SC(normalized_maps, V8.NormalizedMaps)                              \
+  SC(max_map_cache_length, V8.MaxMapCacheLength)                      \
+  SC(map_cache_hits, V8.MapCacheHits)                                 \
+  SC(map_cache_misses, V8.MapCacheMisses)                             \
   SC(props_to_dictionary, V8.ObjectPropertiesToDictionary)            \
   SC(elements_to_dictionary, V8.ObjectElementsToDictionary)           \
   SC(alive_after_last_gc, V8.AliveAfterLastGC)                        \
   SC(objs_since_last_young, V8.ObjsSinceLastYoung)                    \
   SC(objs_since_last_full, V8.ObjsSinceLastFull)                      \
   SC(symbol_table_capacity, V8.SymbolTableCapacity)                   \
   SC(number_of_symbols, V8.NumberOfSymbols)                           \
   SC(script_wrappers, V8.ScriptWrappers)                              \
   SC(call_initialize_stubs, V8.CallInitializeStubs)                   \
   SC(call_premonomorphic_stubs, V8.CallPreMonomorphicStubs)           \
@@ skipping 226 matching lines @@
   // Sliding state window counters.
   StatsCounter state_counters_[kSlidingStateWindowCounterCount];
   friend class Isolate;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Counters);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_V8_COUNTERS_H_