dart2dart: Copy propagation in dart_tree.

sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
index 8b168c1cf3882014c288ddd1a4403f3b7ff2fa15..18aaff06bbacfaf4cd4d98694ea19d88ab79e42d 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
@@ -237,10 +237,10 @@ class DartBackend extends Backend {
         compiler.tracer.traceCompilation(element.name, null, compiler);
         compiler.tracer.traceGraph('Tree builder', definition);
         TreeElementMapping treeElements = new TreeElementMapping(element);
-        new tree.CopyPropagateClosureVariables().rewrite(definition);
-        compiler.tracer.traceGraph('Copy propagate closure vars', definition);
         new tree.StatementRewriter().rewrite(definition);
         compiler.tracer.traceGraph('Statement rewriter', definition);
+        new tree.CopyPropagator().rewrite(definition);
+        compiler.tracer.traceGraph('Copy propagation', definition);
         new tree.LoopRewriter().rewrite(definition);
         compiler.tracer.traceGraph('Loop rewriter', definition);
         new tree.LogicalRewriter().rewrite(definition);