[heap] Move {hidden_string} into the root list.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 20 matching lines @@
   V(Map, one_pointer_filler_map, OnePointerFillerMap)                          \
   V(Map, two_pointer_filler_map, TwoPointerFillerMap)                          \
   /* Cluster the most popular ones in a few cache lines here at the top.    */ \
   V(Smi, store_buffer_top, StoreBufferTop)                                     \
   V(Oddball, undefined_value, UndefinedValue)                                  \
   V(Oddball, the_hole_value, TheHoleValue)                                     \
   V(Oddball, null_value, NullValue)                                            \
   V(Oddball, true_value, TrueValue)                                            \
   V(Oddball, false_value, FalseValue)                                          \
   V(String, empty_string, empty_string)                                        \
+  V(String, hidden_string, hidden_string)                                      \
   V(Oddball, uninitialized_value, UninitializedValue)                          \
   V(Map, cell_map, CellMap)                                                    \
   V(Map, global_property_cell_map, GlobalPropertyCellMap)                      \
   V(Map, shared_function_info_map, SharedFunctionInfoMap)                      \
   V(Map, meta_map, MetaMap)                                                    \
   V(Map, heap_number_map, HeapNumberMap)                                       \
   V(Map, mutable_heap_number_map, MutableHeapNumberMap)                        \
   V(Map, float32x4_map, Float32x4Map)                                          \
   V(Map, int32x4_map, Int32x4Map)                                              \
   V(Map, bool32x4_map, Bool32x4Map)                                            \
@@ skipping 864 matching lines @@
 #undef STRING_ACCESSOR
 
 #define SYMBOL_ACCESSOR(name) inline Symbol* name();
   PRIVATE_SYMBOL_LIST(SYMBOL_ACCESSOR)
 #undef SYMBOL_ACCESSOR
 
 #define SYMBOL_ACCESSOR(name, varname, description) inline Symbol* name();
   PUBLIC_SYMBOL_LIST(SYMBOL_ACCESSOR)
 #undef SYMBOL_ACCESSOR
 
-  // The hidden_string is special because it is the empty string, but does
-  // not match the empty string.
-  String* hidden_string() { return hidden_string_; }
-
   void set_native_contexts_list(Object* object) {
     native_contexts_list_ = object;
   }
   Object* native_contexts_list() const { return native_contexts_list_; }
 
   void set_allocation_sites_list(Object* object) {
     allocation_sites_list_ = object;
   }
   Object* allocation_sites_list() { return allocation_sites_list_; }
 
@@ skipping 862 matching lines @@
   struct StructTable {
     InstanceType type;
     int size;
     RootListIndex index;
   };
 
   static const StringTypeTable string_type_table[];
   static const ConstantStringTable constant_string_table[];
   static const StructTable struct_table[];
 
-  // The special hidden string which is an empty string, but does not match
-  // any string when looked up in properties.
-  String* hidden_string_;
-
   void AddPrivateGlobalSymbols(Handle<Object> private_intern_table);
 
   struct GCCallbackPair {
     GCCallbackPair(v8::Isolate::GCCallback callback, GCType gc_type,
                    bool pass_isolate)
         : callback(callback), gc_type(gc_type), pass_isolate(pass_isolate) {}
 
     bool operator==(const GCCallbackPair& other) const {
       return other.callback == callback;
     }
@@ skipping 878 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_