Need to regen cached_patches; new class exposed.

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 e2841188d64345867241a23bc62d429e09bee0dd..9dd58913bee6fce694c84c1820b2c1c5e7f284ac 100644
--- a/sdk/lib/js/dartium/cached_patches.dart
+++ b/sdk/lib/js/dartium/cached_patches.dart
@@ -982,6 +982,15 @@ class DomTokenListImpl extends DomTokenList implements js_library.JSObjectInterf
   get runtimeType => DomTokenList;
   toString() => super.toString();
 }
+@patch class DragEvent {
+  static Type get instanceRuntimeType => DragEventImpl;
+
+}
+class DragEventImpl extends DragEvent implements js_library.JSObjectInterfacesDom {
+  DragEventImpl.internal_() : super.internal_();
+  get runtimeType => DragEvent;
+  toString() => super.toString();
+}
 @patch class EffectModel {
   static Type get instanceRuntimeType => EffectModelImpl;