Allow [path.fromUri] to take a string as well as a URI.

pkg/path/lib/src/context.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 path.context;
 
 import 'style.dart';
 import 'parsed_path.dart';
 import 'path_exception.dart';
 import '../path.dart' as p;
@@ skipping 405 matching lines @@
     for (var i = parsed.parts.length - 1; i >= 0; i--) {
       if (!parsed.parts[i].isEmpty) {
         parsed.parts[i] = parsed.basenameWithoutExtension;
         break;
       }
     }
 
     return parsed.toString();
   }
 
-  /// Returns the path represented by [uri].
+  /// Returns the path represented by [uri], which may be a [String] or a [Uri].
   ///
   /// For POSIX and Windows styles, [uri] must be a `file:` URI. For the URL
   /// style, this will just convert [uri] to a string.
   ///
   ///     // POSIX
-  ///     context.fromUri(Uri.parse('file:///path/to/foo'))
+  ///     context.fromUri('file:///path/to/foo')
   ///       // -> '/path/to/foo'
   ///
   ///     // Windows
-  ///     context.fromUri(Uri.parse('file:///C:/path/to/foo'))
+  ///     context.fromUri('file:///C:/path/to/foo')
   ///       // -> r'C:\path\to\foo'
   ///
   ///     // URL
-  ///     context.fromUri(Uri.parse('http://dartlang.org/path/to/foo'))
+  ///     context.fromUri('http://dartlang.org/path/to/foo')
   ///       // -> 'http://dartlang.org/path/to/foo'
-  String fromUri(Uri uri) => style.pathFromUri(uri);
+  ///
+  /// If [uri] is relative, a relative path will be returned.
+  ///
+  ///     path.fromUri('path/to/foo'); // -> 'path/to/foo'
+  String fromUri(uri) {
+    if (uri is String) uri = Uri.parse(uri);
+    return style.pathFromUri(uri);
+  }
 
   /// Returns the URI that represents [path].
   ///
   /// For POSIX and Windows styles, this will return a `file:` URI. For the URL
   /// style, this will just convert [path] to a [Uri].
   ///
   ///     // POSIX
   ///     context.toUri('/path/to/foo')
   ///       // -> Uri.parse('file:///path/to/foo')
   ///
@@ skipping 30 matching lines @@
     // Show the arguments.
     var message = new StringBuffer();
     message.write("$method(");
     message.write(args.take(numArgs)
         .map((arg) => arg == null ? "null" : '"$arg"')
         .join(", "));
     message.write("): part ${i - 1} was null, but part $i was not.");
     throw new ArgumentError(message.toString());
   }
 }