Move html events generation to domimpl.

lib/dom/templates/html/dartium/html_dartium.darttemplate

Index: lib/dom/templates/html/dartium/html_dartium.darttemplate
diff --git a/lib/dom/templates/html/dartium/html_dartium.darttemplate b/lib/dom/templates/html/dartium/html_dartium.darttemplate
index c2e79ebc6d0ba48326257bda319c3151cd356093..5991e3a77c81a34bf8b426f530c4f7d96518258e 100644
--- a/lib/dom/templates/html/dartium/html_dartium.darttemplate
+++ b/lib/dom/templates/html/dartium/html_dartium.darttemplate
@@ -66,6 +66,8 @@ _unwrap(raw) {
   return raw is _DOMTypeBase ? raw._ptr : raw;
 }
 
+unwrap_internal(raw) => _unwrap(raw);
+
 // Warning: does not attempt wrap event listeners.
 _wrap(raw) {
   if (raw is! dom.DOMType) return raw;
@@ -83,6 +85,8 @@ $WRAPCASES
   }
 }
 
+wrap_internal(raw) => _wrap(raw);
+
 spawnDomIsolate(Window targetWindow, String entryPoint) =>
   dom.spawnDomIsolate(_unwrap(targetWindow), entryPoint);