Replace HeapNumber as doublebox with an explicit MutableHeapNumber.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 81ecb890bf9c22551202bb6b2e51d19c0abd10ac..f920a6529926df8dbe72e54d36fed421cf586dbf 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -7504,6 +7504,7 @@ class HLoadFieldByIndex V8_FINAL : public HTemplateInstruction<2> {
                     HValue* index) {
     SetOperandAt(0, object);
     SetOperandAt(1, index);
+    SetChangesFlag(kNewSpacePromotion);
     set_representation(Representation::Tagged());
   }