dart2js cps: Remove dart2dart from cps pipeline and clean up.

tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart

Index: tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart
diff --git a/tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart b/tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart
index 163e58d89f9f6f2775e9bdcdd5d4d60c017d6dee..505901f3d04d403be84d8dd7860be6f250ece2a0 100644
--- a/tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart
+++ b/tests/compiler/dart2js/js_backend_cps_ir_source_information_test.dart
@@ -43,7 +43,7 @@ js.Node getJsNodeForElement(Compiler compiler, Element element) {
   return compiler.enqueuer.codegen.generatedCode[element];
 }
 
-ir.RootNode getIrNodeForElement(Compiler compiler, Element element) {
+ir.FunctionDefinition getIrNodeForElement(Compiler compiler, Element element) {
   return compiler.irBuilder.getIr(element);
 }