Add support for if, while, break, continue to js-cps

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';
 
@@ skipping 170 matching lines @@
     traceGraph('Logical rewriter', treeNode);
     new backend_ast_emitter.UnshadowParameters().unshadow(treeNode);
     traceGraph('Unshadow parameters', treeNode);
     return treeNode;
   }
 
   js.Fun compileToJavaScript(CodegenWorkItem work,
                              tree_ir.FunctionDefinition definition) {
     CodeGenerator codeGen = new CodeGenerator(glue, work.registry);
 
-    codeGen.buildFunction(definition);
-    return buildJavaScriptFunction(work.element,
-                                   codeGen.parameters,
-                                   codeGen.body);
+    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) {
     // TODO(sra): Attaching positions might be cleaner if the source position
     // was on a wrapping node.
@@ skipping 21 matching lines @@
       endSourcePosition =
           new TokenSourceFileLocation(sourceFile, endToken, name);
     }
     return node.withPosition(sourcePosition, endSourcePosition);
   }
 
   SourceFile sourceFileOfElement(Element element) {
     return element.implementation.compilationUnit.script.file;
   }
 
-  js.Fun buildJavaScriptFunction(FunctionElement element,
-                                 List<js.Parameter> parameters,
-                                 js.Block body) {
-    return attachPosition(new js.Fun(parameters, body), element);
-  }
 }