Add support for loading scripts from http

runtime/bin/builtin.dart

 // 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.
 
 library builtin;
 
 // Corelib 'print' implementation.
 void _print(arg) {
   _Logger._printString(arg.toString());
 }
@@ skipping 88 matching lines @@
   switch (uri.scheme) {
     case 'file':
       path = _filePathFromFileUri(uri);
       break;
     case 'dart-ext':
       path = _filePathFromOtherUri(uri);
       break;
     case 'package':
       path = _filePathFromPackageUri(uri);
       break;
+    case 'http':
+      path = _filePathFromHttpUri(uri);
+      break;
     default:
       // Only handling file and package URIs in standalone binary.
       _logResolution("# Unknown scheme (${uri.scheme}) in $uri.");
       throw "Not a known scheme: $uri";
   }
 
   if (isWindows && path.startsWith("/")) {
     // For Windows we need to massage the paths a bit according to
     // http://blogs.msdn.com/b/ie/archive/2006/12/06/file-uris-in-windows.aspx
     //
@@ skipping 36 matching lines @@
   var path;
   if (_packageRoot != null) {
     path = "${_packageRoot}${uri.path}";
   } else {
     path = _entrypoint.resolve('packages/${uri.path}').path;
   }
 
   _logResolution("# Package: $path");
   return path;
 }
+
+String _filePathFromHttpUri(Uri uri) {
+  _logResolution('# Path: $uri');
+  return uri.toString();
+}
+
+String _pathFromHttpUri(String userUri) {
+  var uri = Uri.parse(userUri);
+  return uri.path;
+}
+
+String _domainFromHttpUri(String userUri) {
+  var uri = Uri.parse(userUri);
+  return uri.domain;
+}
+
+int _portFromHttpUri(String userUri) {
+  var uri = Uri.parse(userUri);
+  return uri.port == 0 ? 80 : uri.port;
+}