Make the stack_trace package print relative URLs for browser paths.

pkg/stack_trace/lib/src/frame.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 frame;
 
 
 import 'package:path/path.dart' as path;
 
 import 'trace.dart';
@@ skipping 51 matching lines @@
 
   /// Whether this stack frame comes from the Dart core libraries.
   bool get isCore => uri.scheme == 'dart';
 
   /// Returns a human-friendly description of the library that this stack frame
   /// comes from.
   ///
   /// This will usually be the string form of [uri], but a relative URI will be
   /// used if possible.
   String get library {
-    if (uri.scheme != 'file') return uri.toString();
+    if (uri.scheme != Uri.base.scheme) return uri.toString();
+    if (path.style == path.Style.url) return path.relative(uri.toString());
     return path.relative(path.fromUri(uri));
   }
 
   /// Returns the name of the package this stack frame comes from, or `null` if
   /// this stack frame doesn't come from a `package:` URL.
   String get package {
     if (uri.scheme != 'package') return null;
     return uri.path.split('/').first;
   }
 
@@ skipping 161 matching lines @@
     // their stack frames. However, if we do get a relative path, we should
     // handle it gracefully.
     if (uriOrPath.contains('\\')) return path.windows.toUri(uriOrPath);
     return Uri.parse(uriOrPath);
   }
 
   Frame(this.uri, this.line, this.column, this.member);
 
   String toString() => '$location in $member';
 }