Replace HeapNumber as doublebox with an explicit MutableHeapNumber.

src/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_H_
 #define V8_HEAP_H_
 
 #include <cmath>
 
 #include "src/allocation.h"
@@ skipping 24 matching lines @@
   V(Oddball, null_value, NullValue)                                            \
   V(Oddball, true_value, TrueValue)                                            \
   V(Oddball, false_value, FalseValue)                                          \
   V(Oddball, uninitialized_value, UninitializedValue)                          \
   V(Oddball, exception, Exception)                                             \
   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, native_context_map, NativeContextMap)                                 \
   V(Map, fixed_array_map, FixedArrayMap)                                       \
   V(Map, code_map, CodeMap)                                                    \
   V(Map, scope_info_map, ScopeInfoMap)                                         \
   V(Map, fixed_cow_array_map, FixedCOWArrayMap)                                \
   V(Map, fixed_double_array_map, FixedDoubleArrayMap)                          \
   V(Map, constant_pool_array_map, ConstantPoolArrayMap)                        \
   V(Oddball, no_interceptor_result_sentinel, NoInterceptorResultSentinel)      \
   V(Map, hash_table_map, HashTableMap)                                         \
   V(Map, ordered_hash_table_map, OrderedHashTableMap)                          \
@@ skipping 168 matching lines @@
   V(the_hole_value)                       \
   V(null_value)                           \
   V(true_value)                           \
   V(false_value)                          \
   V(uninitialized_value)                  \
   V(cell_map)                             \
   V(global_property_cell_map)             \
   V(shared_function_info_map)             \
   V(meta_map)                             \
   V(heap_number_map)                      \
+  V(mutable_heap_number_map)              \
   V(native_context_map)                   \
   V(fixed_array_map)                      \
   V(code_map)                             \
   V(scope_info_map)                       \
   V(fixed_cow_array_map)                  \
   V(fixed_double_array_map)               \
   V(constant_pool_array_map)              \
   V(no_interceptor_result_sentinel)       \
   V(hash_table_map)                       \
   V(ordered_hash_table_map)               \
@@ skipping 1210 matching lines @@
   // Passing an allocation site means that a memento will be created that
   // points to the site.
   MUST_USE_RESULT AllocationResult AllocateJSObjectFromMap(
       Map* map,
       PretenureFlag pretenure = NOT_TENURED,
       bool alloc_props = true,
       AllocationSite* allocation_site = NULL);
 
   // Allocated a HeapNumber from value.
   MUST_USE_RESULT AllocationResult AllocateHeapNumber(
-      double value, PretenureFlag pretenure = NOT_TENURED);
+      double value,
+      MutableMode mode = IMMUTABLE,
+      PretenureFlag pretenure = NOT_TENURED);
 
   // Allocate a byte array of the specified length
   MUST_USE_RESULT AllocationResult AllocateByteArray(
       int length,
       PretenureFlag pretenure = NOT_TENURED);
 
   // Allocates an arguments object - optionally with an elements array.
   MUST_USE_RESULT AllocationResult AllocateArgumentsObject(
       Object* callee, int length);
 
@@ skipping 1291 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_