Regenerate pub sources.

sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart

Index: sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart b/sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart
index b516cd7ea0912c33a996c9649080ec3ca2fbe3a8..8fdd04788b4df97719f2c15708fda8b6dd3951e9 100644
--- a/sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/barback/cycle_exception.dart
@@ -1,10 +1,33 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 pub.barback.cycle_exception;
+
 import '../exceptions.dart';
+
+/// An exception thrown when a transformer dependency cycle is detected.
+///
+/// A cycle exception is usually produced within a deeply-nested series of
+/// calls. The API is designed to make it easy for each of these calls to add to
+/// the message so that the full reasoning for the cycle is made visible to the
+/// user.
+///
+/// Each call's individual message is called a "step". A [CycleException] is
+/// represented internally as a linked list of steps.
 class CycleException implements ApplicationException {
+  /// The step for this exception.
   final String _step;
+
+  /// The next exception in the linked list.
+  ///
+  /// [_next]'s steps come after [_step].
   final CycleException _next;
+
+  /// A list of all steps in the cycle.
   List<String> get steps {
     if (_step == null) return [];
+
     var exception = this;
     var steps = [];
     while (exception != null) {
@@ -13,17 +36,25 @@ class CycleException implements ApplicationException {
     }
     return steps;
   }
+
   String get message {
     var steps = this.steps;
     if (steps.isEmpty) return "Transformer cycle detected.";
     return "Transformer cycle detected:\n" +
         steps.map((step) => "  $step").join("\n");
   }
-  CycleException([this._step]) : _next = null;
+
+  /// Creates a new [CycleException] with zero or one steps.
+  CycleException([this._step])
+      : _next = null;
+
   CycleException._(this._step, this._next);
+
+  /// Returns a copy of [this] with [step] added to the beginning of [steps].
   CycleException prependStep(String step) {
     if (_step == null) return new CycleException(step);
     return new CycleException._(step, this);
   }
+
   String toString() => message;
 }