ES6 symbols: Introduce Symbol class, along with abstract Name class

src/heap.h

 // Copyright 2012 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 69 matching lines @@
   /* is being compacted.                                                    */ \
   V(FixedArray, number_string_cache, NumberStringCache)                        \
   V(Object, instanceof_cache_function, InstanceofCacheFunction)                \
   V(Object, instanceof_cache_map, InstanceofCacheMap)                          \
   V(Object, instanceof_cache_answer, InstanceofCacheAnswer)                    \
   V(FixedArray, single_character_string_cache, SingleCharacterStringCache)     \
   V(FixedArray, string_split_cache, StringSplitCache)                          \
   V(FixedArray, regexp_multiple_cache, RegExpMultipleCache)                    \
   V(Object, termination_exception, TerminationException)                       \
   V(Smi, hash_seed, HashSeed)                                                  \
+  V(Map, symbol_map, SymbolMap)                                                \
   V(Map, string_map, StringMap)                                                \
   V(Map, ascii_string_map, AsciiStringMap)                                     \
   V(Map, cons_string_map, ConsStringMap)                                       \
   V(Map, cons_ascii_string_map, ConsAsciiStringMap)                            \
   V(Map, sliced_string_map, SlicedStringMap)                                   \
   V(Map, sliced_ascii_string_map, SlicedAsciiStringMap)                        \
   V(Map, external_string_map, ExternalStringMap)                               \
   V(Map, external_string_with_ascii_data_map, ExternalStringWithAsciiDataMap)  \
   V(Map, external_ascii_string_map, ExternalAsciiStringMap)                    \
   V(Map, short_external_string_map, ShortExternalStringMap)                    \
@@ skipping 734 matching lines @@
   // Allocates an external array of the specified length and type.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
   MUST_USE_RESULT MaybeObject* AllocateExternalArray(
       int length,
       ExternalArrayType array_type,
       void* external_pointer,
       PretenureFlag pretenure);
 
+  // Allocate a symbol.
+  // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
+  // failed.
+  // Please note this does not perform a garbage collection.
+  MUST_USE_RESULT MaybeObject* AllocateSymbol(
+      PretenureFlag pretenure = NOT_TENURED);
+
   // Allocate a tenured JS global property cell.
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
   MUST_USE_RESULT MaybeObject* AllocateJSGlobalPropertyCell(Object* value);
 
   // Allocates a fixed array initialized with undefined values
   // Returns Failure::RetryAfterGC(requested_bytes, space) if the allocation
   // failed.
   // Please note this does not perform a garbage collection.
@@ skipping 2096 matching lines @@
   AssertNoAllocation no_alloc;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_