Support default constructors in analyzer2dart.

tests/compiler/dart2js/backend_dart/sexpr2_test.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.
 
 /// Unittest test of the CPS ir generated by the dart2dart compiler.
 library dart_backend.sexpr2_test;
 
 import 'package:compiler/src/dart2jslib.dart';
+import 'package:compiler/src/cps_ir/cps_ir_nodes.dart';
 import 'package:compiler/src/cps_ir/cps_ir_nodes_sexpr.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:expect/expect.dart';
 
 import '../../../../pkg/analyzer2dart/test/test_helper.dart';
 import '../../../../pkg/analyzer2dart/test/sexpr_data.dart';
 
 import 'test_helper.dart';
 
-main() {
-  performTests(TEST_DATA, asyncTester, (TestSpec result) {
-    return compilerFor(result.input).then((Compiler compiler) {
-      void checkOutput(String elementName,
-                       Element element,
-                       String expectedOutput) {
+main(List<String> args) {
+  performTests(TEST_DATA, asyncTester, runTest, args);
+}
+
+runTest(TestSpec result) {
+  return compilerFor(result.input).then((Compiler compiler) {
+    void checkOutput(String elementName,
+                     Element element,
+                     String expectedOutput) {
+      ExecutableDefinition ir = compiler.irBuilder.getIr(element);
+      if (expectedOutput == null) {
+        Expect.isNull(ir, "\nInput:\n${result.input}\n"
+                          "No CPS IR expected for $element");
+      } else {
+        Expect.isNotNull(ir, "\nInput:\n${result.input}\n"
+                             "No CPS IR for $element");
         expectedOutput = expectedOutput.trim();
-        String output = compiler.irBuilder.getIr(element)
-            .accept(new SExpressionStringifier()).trim();
+        String output = ir.accept(new SExpressionStringifier()).trim();
         Expect.equals(expectedOutput, output,
             "\nInput:\n${result.input}\n"
             "Expected for '$elementName':\n$expectedOutput\n"
             "Actual for '$elementName':\n$output\n");
       }
+    }
 
-      if (result.output is String) {
-        checkOutput('main', compiler.mainFunction, result.output);
-      } else {
-        assert(result.output is Map<String, String>);
-        result.output.forEach((String elementName, String output) {
-          Element element;
-          if (elementName.contains('.')) {
-            ClassElement cls = compiler.mainApp.localLookup(
-                elementName.substring(0, elementName.indexOf('.')));
-            element = cls.localLookup(
-                elementName.substring(elementName.indexOf('.') + 1));
-          } else {
-            element = compiler.mainApp.localLookup(elementName);
-          }
-          checkOutput(elementName, element, output);
-        });
-      }
-    });
+    if (result.output is String) {
+      checkOutput('main', compiler.mainFunction, result.output);
+    } else {
+      assert(result.output is Map<String, String>);
+      result.output.forEach((String elementName, String output) {
+        Element element;
+        if (elementName.contains('.')) {
+          ClassElement cls = compiler.mainApp.localLookup(
+              elementName.substring(0, elementName.indexOf('.')));
+          element = cls.localLookup(
+              elementName.substring(elementName.indexOf('.') + 1));
+        } else {
+          element = compiler.mainApp.localLookup(elementName);
+        }
+        checkOutput(elementName, element, output);
+      });
+    }
   });
 }