Add support for file URIs and extracting the file path from file URIs

tests/standalone/io/uri_platform_test.dart

Index: tests/standalone/io/uri_platform_test.dart
diff --git a/tests/standalone/io/uri_platform_test.dart b/tests/standalone/io/uri_platform_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..599f2a8aa26733c4f5a6d5a9d93272a7054c1391
--- /dev/null
+++ b/tests/standalone/io/uri_platform_test.dart
@@ -0,0 +1,39 @@
+// Copyright (c) 2012, 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 "package:expect/expect.dart";
+import "dart:io";
+
+main() {
+  if (Platform.isWindows) {
+    Expect.equals("a\\b", Uri.parse("a/b").toFilePath());
+    Expect.equals("a\\b\\", Uri.parse("a/b/").toFilePath());
+    Expect.equals("a b", Uri.parse("a%20b").toFilePath());
+    Expect.equals("\\a b", Uri.parse("file:///a%20b").toFilePath());
+    Expect.equals("\\a\\b", Uri.parse("file:///a/b").toFilePath());
+    Expect.equals("C:\\", Uri.parse("file:///C:").toFilePath());
+    Expect.equals("C:\\", Uri.parse("file:///C:/").toFilePath());
+    Expect.equals("\\\\host\\a\\b", Uri.parse("file://host/a/b").toFilePath());
+
+    Expect.equals("a\\b", new Uri.file("a/b").toFilePath());
+    Expect.equals("a\\b", new Uri.file("a\\b").toFilePath());
+    Expect.equals("\\a\\b", new Uri.file("/a/b").toFilePath());
+    Expect.equals("\\a\\b", new Uri.file("\\a\\b").toFilePath());
+    Expect.equals("\\a\\b", new Uri.file("\\a/b").toFilePath());
+    Expect.equals("\\a\\b", new Uri.file("/a\\b").toFilePath());
+  } else {
+    Expect.equals("a/b", Uri.parse("a/b").toFilePath());
+    Expect.equals("a/b/", Uri.parse("a/b/").toFilePath());
+    Expect.equals("a b", Uri.parse("a%20b").toFilePath());
+    Expect.equals("/a b", Uri.parse("file:///a%20b").toFilePath());
+    Expect.equals("/a/b", Uri.parse("file:///a/b").toFilePath());
+    Expect.equals("/C:", Uri.parse("file:///C:").toFilePath());
+    Expect.equals("/C:/", Uri.parse("file:///C:/").toFilePath());
+    Expect.throws(() => Uri.parse("file://host/a/b").toFilePath(),
+                  (e) => e is UnsupportedError);
+
+    Expect.equals("a/b", new Uri.file("a/b").toFilePath());
+    Expect.equals("a\\b", new Uri.file("a\\b").toFilePath());
+  }
+}