Get rid of all the library tags.

lib/src/backend/test_platform.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.
 
-library test.backend.test_platform;
-
 // TODO(nweiz): support pluggable platforms.
 /// An enum of all platforms on which tests can run.
 class TestPlatform {
   // When adding new platforms, be sure to update the baseline and derived
   // variable tests in test/backend/platform_selector/evaluate_test.
 
   /// The command-line Dart VM.
   static const TestPlatform vm =
       const TestPlatform._("VM", "vm", isDartVM: true);
 
@@ skipping 67 matching lines @@
 
   /// Whether this platform has no visible window.
   final bool isHeadless;
 
   const TestPlatform._(this.name, this.identifier, {this.isDartVM: false,
       this.isBrowser: false, this.isJS: false, this.isBlink: false,
       this.isHeadless: false});
 
   String toString() => name;
 }