Generate all runtime files from dart.

tool/input_sdk/private/errors.dart

+// Copyright (c) 2015, 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.
+part of dart._runtime;
+
+throwCastError(actual, type) => JS('', '''(() => {
+  $throw_(new $CastErrorImplementation($actual, $type));
+})()''');
+
+throwAssertionError() => JS('', '''(() => {
+  $throw_(new $AssertionError());
+})()''');
+
+throwNullValueError() => JS('', '''(() => {
+  // TODO(vsm): Per spec, we should throw an NSM here.  Technically, we ought
+  // to thread through method info, but that uglifies the code and can't
+  // actually be queried ... it only affects how the error is printed.
+  $throw_(new $NoSuchMethodError(null,
+      new $Symbol('<Unexpected Null Value>'), null, null, null));
+})()''');