Remove files that have already been ported or do not need to be ported.

client/html/src/LoseContextWrappingImplementation.dart

Index: client/html/src/LoseContextWrappingImplementation.dart
diff --git a/client/html/src/LoseContextWrappingImplementation.dart b/client/html/src/LoseContextWrappingImplementation.dart
deleted file mode 100644
index bcb82a305b21f87fb2e359ddabc7db61d3af9140..0000000000000000000000000000000000000000
--- a/client/html/src/LoseContextWrappingImplementation.dart
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright (c) 2011, 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.
-
-/** @domName WebGLLoseContext */
-class LoseContextWrappingImplementation extends DOMWrapperBase implements LoseContext {
-  LoseContextWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
-
-  void loseContext() {
-    _ptr.loseContext();
-    return;
-  }
-
-  void restoreContext() {
-    _ptr.restoreContext();
-    return;
-  }
-}