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

sdk/lib/_internal/lib/platform_patch.dart

Index: sdk/lib/_internal/lib/platform_patch.dart
diff --git a/sdk/lib/_internal/lib/platform_patch.dart b/sdk/lib/_internal/lib/platform_patch.dart
index 8df6d946c9c5d72ba154d01612807fdee14cbe56..0a294ef599f54081ed2ae145f51bdbcd97c0d109 100644
--- a/sdk/lib/_internal/lib/platform_patch.dart
+++ b/sdk/lib/_internal/lib/platform_patch.dart
@@ -2,3 +2,50 @@
 // 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 new _PlatformImpl();
+  }
+}
+
+class _PlatformImpl implements _Platform {
+  int get numberOfProcessors {
+    return null;
+  }
+
+  String get pathSeparator {
+    return "/";
+  }
+
+  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;
+  }
+}