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

test/unittests/compiler/simplified-operator-reducer-unittest.cc

Index: test/unittests/compiler/simplified-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/simplified-operator-reducer-unittest.cc b/test/unittests/compiler/simplified-operator-reducer-unittest.cc
index 465ee84b4f037691669fb17d25260e305f96275b..7f8e43d4284e6d9bae2948510b0ba7e4617004ca 100644
--- a/test/unittests/compiler/simplified-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/simplified-operator-reducer-unittest.cc
@@ -22,7 +22,7 @@ class SimplifiedOperatorReducerTest : public GraphTest {
 
  protected:
   Reduction Reduce(Node* node) {
-    MachineOperatorBuilder machine;
+    MachineOperatorBuilder machine(zone());
     JSOperatorBuilder javascript(zone());
     JSGraph jsgraph(graph(), common(), &javascript, &machine);
     SimplifiedOperatorReducer reducer(&jsgraph);