Replace 'the the' with 'the'

pkg/testing/lib/src/chain.dart

 // Copyright (c) 2016, 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.md file.
 
 library testing.chain;
 
 import 'dart:async' show Future, Stream;
 
 import 'dart:convert' show JSON, JsonEncoder;
 
@@ skipping 132 matching lines @@
       Result result;
       // Records the outcome of the last step that was run.
       Step lastStepRun;
 
       /// Performs one step of [iterator].
       ///
       /// If `step.isAsync` is true, the corresponding step is said to be
       /// asynchronous.
       ///
       /// If a step is asynchrouns the future returned from this function will
-      /// complete after the the first asynchronous step is scheduled.  This
+      /// complete after the first asynchronous step is scheduled.  This
       /// allows us to start processing the next test while an external process
       /// completes as steps can be interleaved. To ensure all steps are
       /// completed, wait for [futures].
       ///
       /// Otherwise, the future returned will complete when all steps are
       /// completed. This ensures that tests are run in sequence without
       /// interleaving steps.
       Future doStep(dynamic input) async {
         Future future;
         bool isAsync = false;
@@ skipping 177 matching lines @@
 /// This is called from generated code.
 Future<Null> runChain(CreateContext f, Map<String, String> environment,
     Set<String> selectors, String json) {
   return withErrorHandling(() async {
     Chain suite = new Suite.fromJsonMap(Uri.base, JSON.decode(json));
     print("Running ${suite.name}");
     ChainContext context = await f(suite, environment);
     return context.run(suite, selectors);
   });
 }