Add some user-friendly utility functions to pkg/analyzer_experimental.

pkg/analyzer_experimental/lib/src/utils.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.
+
+import 'dart:io';
+import 'dart:uri';
+
+import 'package:pathos/path.dart' as pathos;
+
+/// Converts a local path string to a `file:` [Uri].
+Uri pathToFileUri(String pathString) {
+  pathString = pathos.absolute(pathString);
+  if (Platform.operatingSystem != 'windows') {
+    return Uri.parse('file://$pathString');
+  } else if (pathos.rootPrefix(pathString).startsWith('\\\\')) {
+    // Network paths become "file://hostname/path/to/file".
+    return Uri.parse('file:${pathString.replaceAll("\\", "/")}');
+  } else {
+    // Drive-letter paths become "file:///C:/path/to/file".
+    return Uri.parse('file:///${pathString.replaceAll("\\", "/")}');
+  }
+}