dart2js cps: Introduce some built-in operators in type propagation.

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 176 matching lines @@
     return true; // So this can be used from assert().
   }
 
   tree_ir.FunctionDefinition optimizeTreeIR(tree_ir.FunctionDefinition node) {
     void applyTreePass(tree_opt.Pass pass) {
       pass.rewrite(node);
       traceGraph(pass.passName, node);
       assert(checkTreeIntegrity(node));
     }
 
-    applyTreePass(new StatementRewriter(isDartMode: false));
+    applyTreePass(new StatementRewriter());
     applyTreePass(new VariableMerger());
     applyTreePass(new LoopRewriter());
     applyTreePass(new LogicalRewriter());
     applyTreePass(new PullIntoInitializers());
 
     return node;
   }
 
   js.Fun compileToJavaScript(CodegenWorkItem work,
                              tree_ir.FunctionDefinition definition) {
     CodeGenerator codeGen = new CodeGenerator(glue, work.registry);
     return attachPosition(codeGen.buildFunction(definition), work.element);
   }
 
   Iterable<CompilerTask> get tasks {
     // 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.forContext(element)
             .buildDeclaration(element));
   }
 }