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

sdk/lib/js/dartium/cached_patches.dart

Index: sdk/lib/js/dartium/cached_patches.dart
diff --git a/sdk/lib/js/dartium/cached_patches.dart b/sdk/lib/js/dartium/cached_patches.dart
index 81edc87afd1731142ccb821f7514f24ce82ad0fd..f9a46f2b180d64529c6e48e0d17f6dff8334b7e5 100644
--- a/sdk/lib/js/dartium/cached_patches.dart
+++ b/sdk/lib/js/dartium/cached_patches.dart
@@ -2644,15 +2644,6 @@ class RelatedEventImpl extends RelatedEvent implements js_library.JSObjectInterf
   get runtimeType => RelatedEvent;
   toString() => super.toString();
 }
-patch class ResourceProgressEvent {
-  static Type get instanceRuntimeType => ResourceProgressEventImpl;
-
-}
-class ResourceProgressEventImpl extends ResourceProgressEvent implements js_library.JSObjectInterfacesDom {
-  ResourceProgressEventImpl.internal_() : super.internal_();
-  get runtimeType => ResourceProgressEvent;
-  toString() => super.toString();
-}
 patch class RtcDataChannel {
   static Type get instanceRuntimeType => RtcDataChannelImpl;
 
@@ -3958,6 +3949,15 @@ class _RequestImpl extends _Request implements js_library.JSObjectInterfacesDom
   get runtimeType => _Request;
   toString() => super.toString();
 }
+patch class _ResourceProgressEvent {
+  static Type get instanceRuntimeType => _ResourceProgressEventImpl;
+
+}
+class _ResourceProgressEventImpl extends _ResourceProgressEvent implements js_library.JSObjectInterfacesDom {
+  _ResourceProgressEventImpl.internal_() : super.internal_();
+  get runtimeType => _ResourceProgressEvent;
+  toString() => super.toString();
+}
 patch class _Response {
   static Type get instanceRuntimeType => _ResponseImpl;