Add toUri and fromUri functions to pathos.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index c67ce5720ec48ecdfaf1757c520407d16ac06c7f..d5210f3d57887889592f05027c36bc629c77ef17 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -376,37 +376,7 @@ Future awaitObject(object) {
 /// be globally unique, or the wrong library path may be returned.
 String libraryPath(String libraryName) {
   var libraries = currentMirrorSystem().findLibrary(new Symbol(libraryName));
-  return fileUriToPath(libraries.single.uri);
-}
-
-/// Converts a `file:` [Uri] to a local path string.
-String fileUriToPath(Uri uri) {
-  if (uri.scheme != 'file') {
-    throw new ArgumentError("Uri $uri must have scheme 'file:'.");
-  }
-  if (Platform.operatingSystem != 'windows') return uri.path;
-  if (uri.path.startsWith("/")) {
-    // Drive-letter paths look like "file:///C:/path/to/file". The replaceFirst
-    // removes the extra initial slash.
-    return uri.path.replaceFirst("/", "").replaceAll("/", "\\");
-  } else {
-    // Network paths look like "file://hostname/path/to/file".
-    return "\\\\${uri.path.replaceAll("/", "\\")}";
-  }
-}
-
-/// Converts a local path string to a `file:` [Uri].
-Uri pathToFileUri(String pathString) {
-  pathString = path.absolute(pathString);
-  if (Platform.operatingSystem != 'windows') {
-    return Uri.parse('file://$pathString');
-  } else if (path.rootPrefix(pathString).startsWith('\\\\')) {
-    // Network paths become "file://hostname/path/to/file".
-    return Uri.parse('file:${pathString.replaceAll("\\", "/")}');
-  } else {
-    // Drive-letter paths become "file:///C:/path/to/file".
-    return Uri.parse('file:///${pathString.replaceAll("\\", "/")}');
-  }
+  return path.fromUri(libraries.single.uri);
 }
 
 /// Gets a "special" string (ANSI escape or Unicode). On Windows, returns