Fix issue https://code.google.com/p/dart/issues/detail?id=8106: save the sourceElement in the one s…

tests/compiler/dart2js/interceptor_test.dart

 // Copyright (c) 2013, 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 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
   foo(a) {
     // Make sure there is a bailout version.
     foo(a);
     // This will make a one shot interceptor that will be optimized in
     // the non-bailout version because we know a is a number.
     return (a + 42).toString;
   }
 """;
 
+const String TEST_TWO = r"""
+  foo(a) {
+    var myVariableName = a + 42;
+    print(myVariableName);
+    print(myVariableName);
+  }
+""";
+
 main() {
   var generated = compile(TEST_ONE, entry: 'foo');
   // Check that the one shot interceptor got converted to a direct
   // call to the interceptor object.
   Expect.isTrue(generated.contains('CONSTANT.get\$toString(a + 42);'));
+
+  // Check that one-shot interceptors preserve variable names, see
+  // https://code.google.com/p/dart/issues/detail?id=8106.
+  generated = compile(TEST_TWO, entry: 'foo');
+  Expect.isTrue(generated.contains('\$.\$\$add(a, 42)'));
+  Expect.isTrue(generated.contains('myVariableName'));
 }