Support top-level field declaration and assignment 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_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) {
-      String expectedOutput = result.output.trim();
-      String output = compiler.irBuilder.getIr(compiler.mainFunction)
-          .accept(new SExpressionStringifier()).trim();
-      Expect.equals(expectedOutput, output,
-          '\nInput:\n${result.input}\n'
-          'Expected:\n$expectedOutput\n'
-          'Actual:\n$output\n');
+      void checkOutput(Element element, String expectedOutput) {
+        expectedOutput = expectedOutput.trim();
+        String output = compiler.irBuilder.getIr(element)
+            .accept(new SExpressionStringifier()).trim();
+        Expect.equals(expectedOutput, output,
+            '\nInput:\n${result.input}\n'
+            'Expected:\n$expectedOutput\n'
+            'Actual:\n$output\n');
+      }
+
+      if (result.output is String) {
+        checkOutput(compiler.mainFunction, result.output);
+      } else {
+        assert(result.output is Map<String, String>);
+        result.output.forEach((String elementName, String output) {
+          checkOutput(compiler.mainApp.localLookup(elementName), output);
+        });
+      }
     });
   });
 }