Add toUri and fromUri functions to pathos.

sdk/lib/_internal/dartdoc/bin/dartdoc.dart

Index: sdk/lib/_internal/dartdoc/bin/dartdoc.dart
diff --git a/sdk/lib/_internal/dartdoc/bin/dartdoc.dart b/sdk/lib/_internal/dartdoc/bin/dartdoc.dart
index c0fdf6e5b7c3d1524087f396bd32410f532b8c1c..cc36155c00bfc5e3b3caa47b6ada6ea2f9dcb8a6 100644
--- a/sdk/lib/_internal/dartdoc/bin/dartdoc.dart
+++ b/sdk/lib/_internal/dartdoc/bin/dartdoc.dart
@@ -214,7 +214,7 @@ mainWithOptions(Options options) {
     var entrypointRoot;
     for (final entrypoint in option.rest) {
       var uri = Uri.parse(entrypoint);
-      if (uri.scheme == '') uri = pathToFileUri(entrypoint);
+      if (uri.scheme == '') uri = path.toUri(entrypoint);
       entrypoints.add(uri);
 
       if (uri.scheme != 'file') continue;
@@ -274,7 +274,7 @@ String _getPackageRoot(List<Uri> entrypoints) {
       orElse: () => null);
   if (fileEntrypoint == null) return;
 
-  var script = path.normalize(path.absolute(fileUriToPath(fileEntrypoint)));
+  var script = path.normalize(path.absolute(path.fromUri(fileEntrypoint)));
   var dir = path.join(path.dirname(script), 'packages/');
   if (new Directory(dir).existsSync()) return dir;