Add cleanup ShrinkingReducer pass after second TypePropagation pass.

pkg/compiler/lib/src/js_backend/codegen/task.dart

Index: pkg/compiler/lib/src/js_backend/codegen/task.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/task.dart b/pkg/compiler/lib/src/js_backend/codegen/task.dart
index a65685abec2eed25b36df588866b19f4e7768d97..6fe5bccb26ef005abd5789db806e694452aa5392 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/task.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/task.dart
@@ -223,6 +223,7 @@ class CpsFunctionCompiler implements FunctionCompiler {
       applyCpsPass(new ShrinkingReducer(), cpsFunction);
       applyCpsPass(new RedundantRefinementEliminator(typeSystem), cpsFunction);
       applyCpsPass(new TypePropagator(this, recomputeAll: true), cpsFunction);
+      applyCpsPass(new ShrinkingReducer(), cpsFunction);
       applyCpsPass(new EagerlyLoadStatics(), cpsFunction);
       applyCpsPass(new GVN(compiler, typeSystem), cpsFunction);
       applyCpsPass(new UpdateRefinements(typeSystem), cpsFunction);