[optimizing] Name the last DCE pass.

This will allow Checker to differentiate between them.

Change-Id: I972d452a64f1c19d370567b9ef3d620f9b835a9a
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index ab752c3..218894f 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -321,7 +321,7 @@
                              PassInfoPrinter* pass_info_printer,
                              StackHandleScopeCollection* handles) {
   HDeadCodeElimination dce1(graph, stats);
-  HDeadCodeElimination dce2(graph, stats);
+  HDeadCodeElimination dce2(graph, stats, "dead_code_elimination_final");
   HConstantFolding fold1(graph);
   InstructionSimplifier simplify1(graph, stats);
   HBooleanSimplifier boolean_not(graph);