Change dart:io Platform.script to return a Uri.

sdk/lib/io/platform_impl.dart

Index: sdk/lib/io/platform_impl.dart
diff --git a/sdk/lib/io/platform_impl.dart b/sdk/lib/io/platform_impl.dart
index 56a586916d04af66c7179bebb6b0398bb6882291..3e018a0e7b669bffa3d8a77869c79361f30ab12c 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -18,6 +18,18 @@ class _Platform {
   static int get numberOfProcessors => _numberOfProcessors();
   static String get pathSeparator => _pathSeparator();
   static String get operatingSystem => _operatingSystem();
+  static Uri script = _script();
+  static Uri _script() {
+    // The embedder (Dart executable) creates the Platform._nativeScript field.
+    var s = Platform._nativeScript;
+    if (s.startsWith('http:') ||
+        s.startsWith('https:') ||
+        s.startsWith('file:')) {
+      return Uri.parse(s);
+    } else {
+      return new Uri.file(s);
+    }
+  }
 
   static String get localHostname {
     var result = _localHostname();