Fix Directory, File and Link constructor text.

sdk/lib/io/link.dart

Index: sdk/lib/io/link.dart
diff --git a/sdk/lib/io/link.dart b/sdk/lib/io/link.dart
index 13c18693f53c39e9a7309526c0f6a3f073920c08..eb65ac818a80385534d7ed6680fe25c44c43ae5a 100644
--- a/sdk/lib/io/link.dart
+++ b/sdk/lib/io/link.dart
@@ -15,9 +15,13 @@ abstract class Link extends FileSystemEntity {
   factory Link(String path) => new _Link(path);
 
   /**
-   * Create a Lint object from a URI.
+   * Creates a [Link] object.
    *
-   * If [uri] cannot reference a link this throws [UnsupportedError].
+   * If [path] is a relative path, it will be interpreted relative to the
+   * current working directory (see [Directory.current]), when used.
+   *
+   * If [path] is an absolute path, it will be immune to changes to the
+   * current working directory.
    */
   factory Link.fromUri(Uri uri) => new Link(uri.toFilePath());