dart2js cps: Add path-sensitive types by inserting refinement IR nodes.

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Generate code using the cps-based IR pipeline.
 library code_generator_task;
 
 import 'glue.dart';
 import 'codegen.dart';
 import 'unsugar.dart';
@@ skipping 152 matching lines @@
   }
 
   cps.FunctionDefinition optimizeCpsIR(cps.FunctionDefinition cpsNode) {
     // Transformations on the CPS IR.
     void applyCpsPass(cps_opt.Pass pass) {
       pass.rewrite(cpsNode);
       traceGraph(pass.passName, cpsNode);
       assert(checkCpsIntegrity(cpsNode));
     }
 
+    applyCpsPass(new InsertRefinements(compiler.typesTask, compiler.world));
     TypePropagator typePropagator = new TypePropagator(compiler, this);
     applyCpsPass(typePropagator);
     dumpTypedIR(cpsNode, typePropagator);
+    applyCpsPass(new RemoveRefinements());
     applyCpsPass(new LoopInvariantCodeMotion());
     applyCpsPass(new ShareInterceptors());
     applyCpsPass(new ScalarReplacer(compiler));
     applyCpsPass(new ShrinkingReducer());
     applyCpsPass(new MutableVariableEliminator());
     applyCpsPass(new RedundantJoinEliminator());
     applyCpsPass(new RedundantPhiEliminator());
     applyCpsPass(new ShrinkingReducer());
     applyCpsPass(new LetSinker());
 
@@ skipping 47 matching lines @@
     // TODO(sigurdm): Make a better list of tasks.
     return <CompilerTask>[irBuilderTask]..addAll(fallbackCompiler.tasks);
   }
 
   js.Node attachPosition(js.Node node, AstElement element) {
     return node.withSourceInformation(
         sourceInformationFactory.createBuilderForContext(element)
             .buildDeclaration(element));
   }
 }