Fix bugs in simplified lowering relating to int32/uint32 signs.

test/cctest/compiler/test-schedule.cc

Index: test/cctest/compiler/test-schedule.cc
diff --git a/test/cctest/compiler/test-schedule.cc b/test/cctest/compiler/test-schedule.cc
index 7b4f9757a6bff2a413f2d72270495e69017e6764..d2a52c7627fdd75480d4435f7b21f94f6a219039 100644
--- a/test/cctest/compiler/test-schedule.cc
+++ b/test/cctest/compiler/test-schedule.cc
@@ -163,7 +163,8 @@ TEST(BuildMulNodeGraph) {
   Schedule schedule(scope.main_zone());
   Graph graph(scope.main_zone());
   CommonOperatorBuilder common(scope.main_zone());
-  MachineOperatorBuilder machine;
+  // TODO(titzer): use test operators.
+  MachineOperatorBuilder machine(scope.main_zone());
 
   Node* start = graph.NewNode(common.Start(0));
   graph.SetStart(start);