Add fields to platform library, implement them on runtime dart.

runtime/lib/platform_patch.dart

 // Copyright (c) 2013, 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.
 
+patch class _PatchWorkaround {
+  /* patch */ static _Platform get _platform {
+    return _platformHook;
+  }
+}
+
+// A non-default _Platform, with real values, is stored here by the embedder.
+_Platform _platformHook = new _DefaultPlatform();
+
+
+class _DefaultPlatform implements _Platform {
+  int get numberOfProcessors {
+    return null;
+  }
+
+  String get pathSeparator {
+    return "/";

[Ivan Posva, 2013/10/25 17:03:48]

null

[Bill Hesse, 2013/10/25 17:50:00]

Are you ok with making this "/" on Dartium, when a Dartium implementation is
added?

+  }
+
+  String get operatingSystem {
+    return null;
+  }
+
+  String get localHostname {
+    return null;
+  }
+
+  String get version {
+    return null;
+  }
+
+  Map get environment {
+    return null;
+  }
+
+  String get script {
+    return null;
+  }
+
+  String get executable {
+    return null;
+  }
+
+  List<String>  get executableArguments {
+    return new List<String>(0);
+  }
+
+  String get packageRoot {
+    return null;
+  }
+}