Infer types of bool/null/string literals.

pkg/front_end/testcases/inference/simple_literal_string.dart

Index: pkg/front_end/testcases/inference/simple_literal_string.dart
diff --git a/pkg/front_end/testcases/inference/simple_literal_string.dart b/pkg/front_end/testcases/inference/simple_literal_string.dart
new file mode 100644
index 0000000000000000000000000000000000000000..09d7f404681da7da70928cf44742a725fdebb546
--- /dev/null
+++ b/pkg/front_end/testcases/inference/simple_literal_string.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2017, 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.md file.
+
+/*@testedFeatures=inference*/
+library test;
+
+var /*@topType=String*/ topSimple = 'aaa';
+var /*@topType=String*/ topInterpolation = 'b $topSimple bbb';
+
+main() {
+  var /*@type=String*/ localSimple = 'ccc';
+  var /*@type=String*/ localInterpolation = 'd $localSimple ddd';
+}