Support parsing empty stack chains.

lib/src/chain.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.
 
 library stack_trace.chain;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' as math;
 
@@ skipping 109 matching lines @@
   /// If [trace] is already a [Chain], it will be returned as-is.
   factory Chain.forTrace(StackTrace trace) {
     if (trace is Chain) return trace;
     if (_currentSpec == null) return new Chain([new Trace.from(trace)]);
     return _currentSpec.chainFor(trace);
   }
 
   /// Parses a string representation of a stack chain.
   ///
   /// Specifically, this parses the output of [Chain.toString].
-  factory Chain.parse(String chain) =>
-    new Chain(chain.split(_gap).map((trace) => new Trace.parseFriendly(trace)));
+  factory Chain.parse(String chain) {
+    if (chain.isEmpty) return new Chain([]);
+    return new Chain(
+        chain.split(_gap).map((trace) => new Trace.parseFriendly(trace)));
+  }
 
   /// Returns a new [Chain] comprised of [traces].
   Chain(Iterable<Trace> traces)
       : traces = new UnmodifiableListView<Trace>(traces.toList());
 
   /// Returns a terser version of [this].
   ///
   /// This calls [Trace.terse] on every trace in [traces], and discards any
   /// trace that contain only internal frames.
   Chain get terse => foldFrames((_) => false, terse: true);
@@ skipping 49 matching lines @@
 
     // Don't call out to [Trace.toString] here because that doesn't ensure that
     // padding is consistent across all traces.
     return traces.map((trace) {
       return trace.frames.map((frame) {
         return '${padRight(frame.location, longest)}  ${frame.member}\n';
       }).join();
     }).join(_gap);
   }
 }