[stubs] Introduce a proper ToBooleanStub.

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/assert-scope.h"
@@ skipping 9528 matching lines @@
 
 // The Oddball describes objects null, undefined, true, and false.
 class Oddball: public HeapObject {
  public:
   // [to_string]: Cached to_string computed at startup.
   DECL_ACCESSORS(to_string, String)
 
   // [to_number]: Cached to_number computed at startup.
   DECL_ACCESSORS(to_number, Object)
 
+  // [to_number]: Cached to_boolean computed at startup.
+  DECL_ACCESSORS(to_boolean, Oddball)
+
   // [typeof]: Cached type_of computed at startup.
   DECL_ACCESSORS(type_of, String)
 
   inline byte kind() const;
   inline void set_kind(byte kind);
 
   // ES6 section 7.1.3 ToNumber for Boolean, Null, Undefined.
   MUST_USE_RESULT static inline Handle<Object> ToNumber(Handle<Oddball> input);
 
   DECLARE_CAST(Oddball)
 
   // Dispatched behavior.
   DECLARE_VERIFIER(Oddball)
 
   // Initialize the fields.
   static void Initialize(Isolate* isolate, Handle<Oddball> oddball,
                          const char* to_string, Handle<Object> to_number,
-                         const char* type_of, byte kind);
+                         bool to_boolean, const char* type_of, byte kind);
 
   // Layout description.
   static const int kToStringOffset = HeapObject::kHeaderSize;
   static const int kToNumberOffset = kToStringOffset + kPointerSize;
-  static const int kTypeOfOffset = kToNumberOffset + kPointerSize;
+  static const int kToBooleanOffset = kToNumberOffset + kPointerSize;
+  static const int kTypeOfOffset = kToBooleanOffset + kPointerSize;
   static const int kKindOffset = kTypeOfOffset + kPointerSize;
   static const int kSize = kKindOffset + kPointerSize;
 
   static const byte kFalse = 0;
   static const byte kTrue = 1;
   static const byte kNotBooleanMask = ~1;
   static const byte kTheHole = 2;
   static const byte kNull = 3;
   static const byte kArgumentsMarker = 4;
   static const byte kUndefined = 5;
@@ skipping 1289 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_