Replace HeapNumber as doublebox with an explicit MutableHeapNumber.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 0868db851d99b97104fbec6613957ec9b41524c6..8712f9d54e863ae91b55742fb5277266b4fc398f 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -1020,10 +1020,12 @@ Handle<Object> Factory::NewNumberFromUint(uint32_t value,
 
 
 Handle<HeapNumber> Factory::NewHeapNumber(double value,
+                                          MutableMode mode,
                                           PretenureFlag pretenure) {
   CALL_HEAP_FUNCTION(
       isolate(),
-      isolate()->heap()->AllocateHeapNumber(value, pretenure), HeapNumber);
+      isolate()->heap()->AllocateHeapNumber(value, mode, pretenure),
+      HeapNumber);
 }