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

sdk/lib/_internal/pub/lib/src/command/build.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 pub.command.build;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as path;
@@ skipping 276 matching lines @@
     // Must depend on the browser package.
     if (!entrypoint.root.immediateDependencies.any(
         (dep) => dep.name == 'browser' && dep.source == 'hosted')) {
       return 0;
     }
 
     // Get all of the subdirectories that contain Dart entrypoints.
     var entrypointDirs = entrypoints
         // Convert the asset path to a native-separated one and get the
         // directory containing the entrypoint.
-        .map((id) => path.dirname(path.joinAll(path.url.split(id.path))))
+        .map((id) => path.dirname(path.fromUri(id.path)))
         // Don't copy files to the top levels of the build directories since
         // the normal lib asset copying will take care of that.
         .where((dir) => dir.contains(path.separator))
         .toSet();
 
     for (var dir in entrypointDirs) {
       // TODO(nweiz): we should put browser JS files next to any HTML file
       // rather than any entrypoint. An HTML file could import an entrypoint
       // that's not adjacent.
       _addBrowserJs(dir, "dart");
@@ skipping 45 matching lines @@
         "end": {
           "line": entry.span.end.line,
           "column": entry.span.end.column
         },
       };
     }
 
     return data;
   }
 }