[turbofan] Add initial support for growing stores.

src/compiler/operation-typer.cc

Index: src/compiler/operation-typer.cc
diff --git a/src/compiler/operation-typer.cc b/src/compiler/operation-typer.cc
index 53c2770864864de5294d62403dfc8110677143da..d50862c61e406fb738a5dfd3c5ed46cf12c8c0c0 100644
--- a/src/compiler/operation-typer.cc
+++ b/src/compiler/operation-typer.cc
@@ -485,7 +485,10 @@ Type* OperationTyper::NumberToUint32(Type* type) {
 
 Type* OperationTyper::NumberSilenceNaN(Type* type) {
   DCHECK(type->Is(Type::Number()));
-  // TODO(turbofan): We should have a dedicated type for the signaling NaN.
+  // TODO(jarin): This is a terrible hack; we definitely need a dedicated type
+  // for the hole (tagged and/or double). Otherwise if the input is the hole
+  // NaN constant, we'd just eliminate this node in JSTypedLowering.
+  if (type->Maybe(Type::NaN())) return Type::Number();
   return type;
 }