Some string optimizations:

src/v8-counters.h

 // Copyright 2007-2008 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 148 matching lines @@
   SC(enum_cache_hits, V8.EnumCacheHits)                               \
   SC(enum_cache_misses, V8.EnumCacheMisses)                           \
   SC(reloc_info_count, V8.RelocInfoCount)                             \
   SC(reloc_info_size, V8.RelocInfoSize)                               \
   SC(zone_segment_bytes, V8.ZoneSegmentBytes)                         \
   SC(compute_entry_frame, V8.ComputeEntryFrame)                       \
   SC(generic_binary_stub_calls, V8.GenericBinaryStubCalls)            \
   SC(generic_binary_stub_calls_regs, V8.GenericBinaryStubCallsRegs)   \
   SC(string_add_runtime, V8.StringAddRuntime)                         \
   SC(string_add_native, V8.StringAddNative)                           \
+  SC(string_add_runtime_ext_to_ascii, V8.StringAddRuntimeExtToAscii)  \
   SC(sub_string_runtime, V8.SubStringRuntime)                         \
   SC(sub_string_native, V8.SubStringNative)                           \
   SC(string_compare_native, V8.StringCompareNative)                   \
   SC(string_compare_runtime, V8.StringCompareRuntime)                 \
   SC(regexp_entry_runtime, V8.RegExpEntryRuntime)                     \
   SC(regexp_entry_native, V8.RegExpEntryNative)                       \
   SC(number_to_string_native, V8.NumberToStringNative)                \
   SC(number_to_string_runtime, V8.NumberToStringRuntime)              \
   SC(math_acos, V8.MathAcos)                                          \
   SC(math_asin, V8.MathAsin)                                          \
@@ skipping 41 matching lines @@
     stats_counter_count
   };
 
   // Sliding state window counters.
   static StatsCounter state_counters[];
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_V8_COUNTERS_H_