Revert "Upgrade to 5.0.71.48"

This reverts commit 8389745919cae02139ddc085a63c00d024269cf2.

Change-Id: Ic5c75c8b3ddaf795972372fbc863a514862953c1
diff --git a/src/compiler/representation-change.cc b/src/compiler/representation-change.cc
index 2f7720b..5dab60f 100644
--- a/src/compiler/representation-change.cc
+++ b/src/compiler/representation-change.cc
@@ -97,6 +97,7 @@
 
 namespace {
 
+// TODO(titzer): should Word64 also be implicitly convertable to others?
 bool IsWord(MachineRepresentation rep) {
   return rep == MachineRepresentation::kWord8 ||
          rep == MachineRepresentation::kWord16 ||
@@ -145,9 +146,6 @@
       return GetWord32RepresentationFor(node, output_rep, output_type);
     case MachineRepresentation::kWord64:
       return GetWord64RepresentationFor(node, output_rep, output_type);
-    case MachineRepresentation::kSimd128:  // Fall through.
-      // TODO(bbudge) Handle conversions between tagged and untagged.
-      break;
     case MachineRepresentation::kNone:
       return node;
   }