Now that GraphChecker has a state, don't re-use it.

Otherwise, we'll see the same ids twice.

Change-Id: Ic9bb801629ff90cc788248528d5260aaaff73675
diff --git a/compiler/optimizing/constant_folding_test.cc b/compiler/optimizing/constant_folding_test.cc
index cad6683..ed7e57b 100644
--- a/compiler/optimizing/constant_folding_test.cc
+++ b/compiler/optimizing/constant_folding_test.cc
@@ -47,9 +47,9 @@
 
   x86::CodeGeneratorX86 codegen(graph);
   HConstantFolding(graph).Run();
-  SSAChecker ssa_checker(&allocator, graph);
-  ssa_checker.Run();
-  ASSERT_TRUE(ssa_checker.IsValid());
+  SSAChecker ssa_checker_cf(&allocator, graph);
+  ssa_checker_cf.Run();
+  ASSERT_TRUE(ssa_checker_cf.IsValid());
 
   StringPrettyPrinter printer_after_cf(graph);
   printer_after_cf.VisitInsertionOrder();
@@ -59,8 +59,9 @@
   check_after_cf(graph);
 
   HDeadCodeElimination(graph).Run();
-  ssa_checker.Run();
-  ASSERT_TRUE(ssa_checker.IsValid());
+  SSAChecker ssa_checker_dce(&allocator, graph);
+  ssa_checker_dce.Run();
+  ASSERT_TRUE(ssa_checker_dce.IsValid());
 
   StringPrettyPrinter printer_after_dce(graph);
   printer_after_dce.VisitInsertionOrder();