Add source mapping info to loops.

tests/compiler/dart2js/source_mapping_test.dart

 // Copyright (c) 2012, 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.
 
 #import('dart:uri');
 
 #import("../../../lib/compiler/implementation/leg.dart");
 #import('../../../lib/compiler/implementation/source_file.dart');
 #import("mock_compiler.dart");
 #import('parser_helper.dart');
@@ skipping 55 matching lines @@
   @staticSend(0);
   NewSend o = new @NewSend();
   @o.dynamicSend(0);
   var closureSend = (x) { print(x); };
   @closureSend(0);
 }
 void staticSend(x) { print(x); }
 class NewSend { void dynamicSend(x) { print(x); } }
 ''';
 
+String LOOP_TEST = '''
+void main() {
+  @for (int i = 0; i < 100; ++i) { print(test(13)); @}
+}
+int test(int x) {
+  int result = 1; @while (result < x) { result <<= 1; @} return result;
+}''';
+
+
 main() {
   // These tests are fragile, since mappings for specific source locations
   // could disappear due to various optimizations like code elimination,
   // function inlining, etc. If you broke the test, please try to rewrite it
   // so that the new code is not optimized, otherwise just remove the marker
   // from problematic location.
   testSourceMapLocations(FUNCTIONS_TEST);
   testSourceMapLocations(RETURN_TEST);
   testSourceMapLocations(NOT_TEST);
   testSourceMapLocations(UNARY_TEST);
   testSourceMapLocations(BINARY_TEST);
   testSourceMapLocations(SEND_TEST);
+  testSourceMapLocations(LOOP_TEST);
 }