Fix spawning a data uri on Windows.

BUG=http://dartbug.com/22943
R=johnmccutchan@google.com

Review URL: https://codereview.chromium.org//1017923003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@44691 260f80e4-7a28-3924-810f-c04153c831b5

runtime/tests/vm/vm.status

@@ -71,9 +71,6 @@ dart/data_uri_failures_test/nomime: RuntimeError, OK
 dart/data_uri_failures_test/nocharset: RuntimeError, OK
 dart/data_uri_failures_test/base64: RuntimeError, OK
 
-[ $runtime == vm && $system == windows ]
-dart/data_uri_spawn_test: Crash # http://dartbug.com/22943
-
 [ $compiler == dart2dart ]
 # Skip until we stabilize language tests.
 *: Skip

sdk/lib/io/platform_impl.dart

@@ -48,6 +48,7 @@ class _Platform {
         path.startsWith('https:') ||
         path.startsWith('package:') ||
         path.startsWith('dart:') ||
+        path.startsWith('data:') ||
         path.startsWith('file:')) {
       script = Uri.parse(path);
     } else {