[turbofan] Eliminate usage of representation dimension of Type.

src/compiler/representation-change.cc

Index: src/compiler/representation-change.cc
diff --git a/src/compiler/representation-change.cc b/src/compiler/representation-change.cc
index c9e995ec505d567407d1ddaa66e85c6dc49a1dec..de57f95df8cf9cd4db143dfa9a3b057fc7ea8b23 100644
--- a/src/compiler/representation-change.cc
+++ b/src/compiler/representation-change.cc
@@ -471,7 +471,8 @@ Node* RepresentationChanger::GetFloat64RepresentationFor(
     if (output_type->Is(Type::Undefined())) {
       return jsgraph()->Float64Constant(
           std::numeric_limits<double>::quiet_NaN());
-    } else if (output_type->Is(Type::TaggedSigned())) {
+
+    } else if (output_rep == MachineRepresentation::kTaggedSigned) {
       node = InsertChangeTaggedSignedToInt32(node);
       op = machine()->ChangeInt32ToFloat64();
     } else if (output_type->Is(Type::Number())) {