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

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

Index: test/unittests/compiler/machine-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/machine-operator-reducer-unittest.cc b/test/unittests/compiler/machine-operator-reducer-unittest.cc
index a62216dfcdf283e512f215909895c490abf9eb8e..065a734e2038257a15ff58de0a048d16987e80d1 100644
--- a/test/unittests/compiler/machine-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/machine-operator-reducer-unittest.cc
@@ -22,7 +22,7 @@ namespace compiler {
 class MachineOperatorReducerTest : public TypedGraphTest {
  public:
   explicit MachineOperatorReducerTest(int num_parameters = 2)
-      : TypedGraphTest(num_parameters) {}
+      : TypedGraphTest(num_parameters), machine_(zone()) {}
 
  protected:
   Reduction Reduce(Node* node) {