fix #379, escape of $ in template strings

test/codegen/misc.dart

 // Copyright (c) 2015, 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.
 
 
 // Codegen dependency order test
 const UNINITIALIZED = const _Uninitialized();
 class _Uninitialized { const _Uninitialized(); }
 
 class Generic<T> {
@@ skipping 13 matching lines @@
   operator==(obj) {
     return obj is Derived && obj.z == z && super == obj;
   }
 }
 
 // string escape tests
 // https://github.com/dart-lang/dev_compiler/issues/227
 bool _isWhitespace(String ch) =>
     ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
 
+const expr = 'foo';
 const _escapeMap = const {
   '\n': r'\n',
   '\r': r'\r',
   '\f': r'\f',
   '\b': r'\b',
   '\t': r'\t',
   '\v': r'\v',
   '\x7F': r'\x7F', // delete
+  '\${${expr}}': ''
 };
 
 
 main() {
   // Number literals in call expressions.
   print(1.toString());
   print(1.0.toString());
   print(1.1.toString());
 
   // Type literals, #184
   dynamic x = 42;
   print(x == dynamic);
   print(x == Generic);
 
   // Should be Generic<dynamic>
   print(new Generic<int>().type);
 
   print(new Derived() == new Derived()); // true
 }