Introduce read buffer for external strings when using charAt (ia32).

src/heap.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 92 matching lines @@
   V(Map, sliced_string_map, SlicedStringMap)                                   \
   V(Map, sliced_ascii_string_map, SlicedAsciiStringMap)                        \
   V(Map, cons_symbol_map, ConsSymbolMap)                                       \
   V(Map, cons_ascii_symbol_map, ConsAsciiSymbolMap)                            \
   V(Map, external_symbol_map, ExternalSymbolMap)                               \
   V(Map, external_symbol_with_ascii_data_map, ExternalSymbolWithAsciiDataMap)  \
   V(Map, external_ascii_symbol_map, ExternalAsciiSymbolMap)                    \
   V(Map, external_string_map, ExternalStringMap)                               \
   V(Map, external_string_with_ascii_data_map, ExternalStringWithAsciiDataMap)  \
   V(Map, external_ascii_string_map, ExternalAsciiStringMap)                    \
+  V(Map, external_buffered_symbol_map, ExternalBufferedSymbolMap)              \
+  V(Map,                                                                       \
+    external_buffered_symbol_with_ascii_data_map,                              \
+    ExternalBufferedSymbolWithAsciiDataMap)                                    \
+  V(Map, external_buffered_ascii_symbol_map, ExternalBufferedAsciiSymbolMap)   \
+  V(Map, external_buffered_string_map, ExternalBufferedStringMap)              \
+  V(Map,                                                                       \
+    external_buffered_string_with_ascii_data_map,                              \
+    ExternalBufferedStringWithAsciiDataMap)                                    \
+  V(Map, external_buffered_ascii_string_map, ExternalBufferedAsciiStringMap)   \
   V(Map, undetectable_string_map, UndetectableStringMap)                       \
   V(Map, undetectable_ascii_string_map, UndetectableAsciiStringMap)            \
   V(Map, external_pixel_array_map, ExternalPixelArrayMap)                      \
   V(Map, external_byte_array_map, ExternalByteArrayMap)                        \
   V(Map, external_unsigned_byte_array_map, ExternalUnsignedByteArrayMap)       \
   V(Map, external_short_array_map, ExternalShortArrayMap)                      \
   V(Map, external_unsigned_short_array_map, ExternalUnsignedShortArrayMap)     \
   V(Map, external_int_array_map, ExternalIntArrayMap)                          \
   V(Map, external_unsigned_int_array_map, ExternalUnsignedIntArrayMap)         \
   V(Map, external_float_array_map, ExternalFloatArrayMap)                      \
@@ skipping 2406 matching lines @@
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG || LIVE_OBJECT_LIST
 
 } }  // namespace v8::internal
 
 #undef HEAP
 
 #endif  // V8_HEAP_H_