Updated tests/compiler/* to use new library syntax.

tests/compiler/dart2js/rewrite_better_user_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.
 // Test that we get rid of duplicate type guards on a field when that
 // field is being gvn'ed.
 
-#import("compiler_helper.dart");
+import 'compiler_helper.dart';
 
 const String TEST = r"""
 class A {
   var field = 52;
   foo() {
     var a = this.field;
     while (a + 42 == 42);
     // This field get should be GVN'ed
     a = this.field;
     while (a + 87 == 87);
     field = 'bar';
   }
 }
 
 main() {
   while (true) new A().foo();
 }
 """;
 
 main() {
   String generated = compileAll(TEST);
   RegExp regexp = const RegExp('foo\\\$0\\\$bailout');
   Iterator matches = regexp.allMatches(generated).iterator();
 
   // We check that there is only one call to the bailout method.
   // One match for the call, one for the definition.
   checkNumberOfMatches(matches, 2);
 }