[turbofan] Make MachineType a pair of enums.

test/unittests/compiler/js-context-relaxation-unittest.cc

Index: test/unittests/compiler/js-context-relaxation-unittest.cc
diff --git a/test/unittests/compiler/js-context-relaxation-unittest.cc b/test/unittests/compiler/js-context-relaxation-unittest.cc
index 51283d8236c3dde6c476588a87032a513176765d..a44bd0278da61a7d5a111c512dfe273cf7f4fe03 100644
--- a/test/unittests/compiler/js-context-relaxation-unittest.cc
+++ b/test/unittests/compiler/js-context-relaxation-unittest.cc
@@ -19,7 +19,8 @@ class JSContextRelaxationTest : public GraphTest {
  protected:
   Reduction Reduce(Node* node, MachineOperatorBuilder::Flags flags =
                                    MachineOperatorBuilder::kNoFlags) {
-    MachineOperatorBuilder machine(zone(), kMachPtr, flags);
+    MachineOperatorBuilder machine(zone(), MachineType::PointerRepresentation(),
+                                   flags);
     JSGraph jsgraph(isolate(), graph(), common(), javascript(), nullptr,
                     &machine);
     // TODO(titzer): mock the GraphReducer here for better unit testing.