[stubs] Introduce a proper ToBooleanStub.

src/heap/heap-inl.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_INL_H_
 #define V8_HEAP_HEAP_INL_H_
 
 #include <cmath>
 
 #include "src/base/platform/platform.h"
@@ skipping 637 matching lines @@
   key.source = source;
   key.name = name;
   results_[index] = result;
 }
 
 
 void Heap::ClearInstanceofCache() {
   set_instanceof_cache_function(Smi::FromInt(0));
 }
 
-
-Object* Heap::ToBoolean(bool condition) {
+Oddball* Heap::ToBoolean(bool condition) {
   return condition ? true_value() : false_value();
 }
 
 
 void Heap::CompletelyClearInstanceofCache() {
   set_instanceof_cache_map(Smi::FromInt(0));
   set_instanceof_cache_function(Smi::FromInt(0));
 }
 
 
@@ skipping 64 matching lines @@
 
 void VerifySmisVisitor::VisitPointers(Object** start, Object** end) {
   for (Object** current = start; current < end; current++) {
     CHECK((*current)->IsSmi());
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_INL_H_