Use UnmodifiableListView to expose read-only lists.

pkg/stack_trace/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:uri';
 import 'dart:math' as math;
 
 import 'frame.dart';
 
 final _patchRegExp = new RegExp(r"-patch$");
 
 /// A stack trace, comprised of a list of stack frames.
 class Trace implements StackTrace {
-  // TODO(nweiz): make this read-only once issue 8321 is fixed.
   /// The stack frames that comprise this stack trace.
   final List<Frame> frames;
 
   /// Returns a human-readable representation of [stackTrace]. If [terse] is
   /// set, this folds together multiple stack frames from the Dart core
   /// libraries, so that only the core library method directly called from user
   /// code is visible (see [Trace.terse]).
   static String format(StackTrace stackTrace, {bool terse: true}) {
     var trace = new Trace.from(stackTrace);
     if (terse) trace = trace.terse;
@@ skipping 29 matching lines @@
   }
 
   /// Parses a string representation of a stack trace.
   ///
   /// [trace] should be formatted in the same way as native stack traces.
   Trace.parse(String trace)
       : this(trace.trim().split("\n").map((line) => new Frame.parse(line)));
 
   /// Returns a new [Trace] comprised of [frames].
   Trace(Iterable<Frame> frames)
-      : frames = frames.toList();
+      : frames = new UnmodifiableListView<Frame>(frames.toList());
 
   // TODO(nweiz): Keep track of which [Frame]s are part of the partial stack
   // trace and only print them.
   /// Returns a string representation of this stack trace.
   ///
   /// This is identical to [toString]. It will not be formatted in the manner of
   /// native stack traces.
   String get stackTrace => toString();
 
   /// Returns a string representation of this stack trace.
@@ skipping 55 matching lines @@
   if (string.length >= length) return string;
 
   var result = new StringBuffer();
   result.write(string);
   for (var i = 0; i < length - string.length; i++) {
     result.write(' ');
   }
 
   return result.toString();
 }