Support parsing empty stack chains.

lib/src/trace.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 trace;
 
 import 'dart:collection';
 import 'dart:math' as math;
 
 import 'chain.dart';
@@ skipping 170 matching lines @@
   Trace.parseSafari6_0(String trace)
       : this(trace.trim().split("\n")
           .where((line) => line != '[native code]')
           .map((line) => new Frame.parseFirefox(line)));
 
   /// Parses this package's string representation of a stack trace.
   ///
   /// This also parses string representations of [Chain]s. They parse to the
   /// same trace that [Chain.toTrace] would return.
   Trace.parseFriendly(String trace)
-      : this(trace.trim().split("\n")
-          // Filter out asynchronous gaps from [Chain]s.
-          .where((line) => !line.startsWith('====='))
-          .map((line) => new Frame.parseFriendly(line)));
+      : this(trace.isEmpty
+            ? []
+            : trace.trim().split("\n")
+                // Filter out asynchronous gaps from [Chain]s.
+                .where((line) => !line.startsWith('====='))
+                .map((line) => new Frame.parseFriendly(line)));
 
   /// Returns a new [Trace] comprised of [frames].
   Trace(Iterable<Frame> frames)
       : frames = new UnmodifiableListView<Frame>(frames.toList());
 
   /// Returns a VM-style [StackTrace] object.
   ///
   /// The return value's [toString] method will always return a string
   /// representation in the Dart VM's stack trace format, regardless of what
   /// platform is being used.
@@ skipping 69 matching lines @@
     // Figure out the longest path so we know how much to pad.
     var longest = frames.map((frame) => frame.location.length)
         .fold(0, math.max);
 
     // Print out the stack trace nicely formatted.
     return frames.map((frame) {
       return '${padRight(frame.location, longest)}  ${frame.member}\n';
     }).join();
   }
 }