Overhaul tree IR visitor and rename IR classes.

pkg/analyzer2dart/test/sexpr_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 analyzer2dart compiler.
 
 import 'mock_sdk.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/sdk.dart';
@@ skipping 24 matching lines @@
   String rootFile = '/root.dart';
   provider.newFile(rootFile, input);
   Source rootSource = driver.setRoot(rootFile);
   FunctionElement entryPoint = driver.resolveEntryPoint(rootSource);
   ClosedWorld world = driver.computeWorld(entryPoint);
   ConvertedWorld convertedWorld = convertWorld(world);
 
   void checkOutput(String elementName,
                    dart2js.Element element,
                    String expectedOutput) {
-    ExecutableDefinition ir = convertedWorld.getIr(element);
+    RootNode ir = convertedWorld.getIr(element);
     if (expectedOutput == null) {
       expect(ir, isNull,
           reason: "\nInput:\n${result.input}\n"
                   "No CPS IR expected for $element");
     } else {
       expect(ir, isNotNull,
           reason: "\nInput:\n${result.input}\n"
                   "No CPS IR for $element");
       expectedOutput = expectedOutput.trim();
       String output = ir.accept(new SExpressionStringifier());
@@ skipping 23 matching lines @@
             found = true;
           }
           names.add(name);
         }
       });
       expect(found, isTrue, reason: "'$elementName' not found in $names.");
     });
   }
 }