Strip unused functionality from dart:html and fix strong mode errors. Switch from blacklisting pure…

sdk/lib/_internal/js_runtime/lib/js_helper.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.
 
 library _js_helper;
 
 import 'dart:_js_embedded_names' show
     DEFERRED_LIBRARY_URIS,
     DEFERRED_LIBRARY_HASHES,
     GET_TYPE_FROM_NAME,
@@ skipping 3335 matching lines @@
   if (!_loadedLibraries.contains(loadId)) {
     throw new DeferredNotLoadedError(uri);
   }
 }
 
 /**
  * Special interface recognized by the compiler and implemented by DOM
  * objects that support integer indexing. This interface is not
  * visible to anyone, and is only injected into special libraries.
  */
-abstract class JavaScriptIndexingBehavior extends JSMutableIndexable {
+abstract class JavaScriptIndexingBehavior<E> extends JSMutableIndexable<E> {
 }
 
 // TODO(lrn): These exceptions should be implemented in core.
 // When they are, remove the 'Implementation' here.
 
 /** Thrown by type assertions that fail. */
 class TypeErrorImplementation extends Error implements TypeError {
   final String message;
 
   /**
@@ skipping 733 matching lines @@
 // unneeded code.
 class _UnreachableError extends AssertionError {
   _UnreachableError();
   String toString() => "Assertion failed: Reached dead code";
 }
 
 @NoInline()
 void assertUnreachable() {
   throw new _UnreachableError();
 }