Hide implementation members in dart:html, dart:js and related libraries

tools/dom/scripts/systemhtml.py

Index: tools/dom/scripts/systemhtml.py
diff --git a/tools/dom/scripts/systemhtml.py b/tools/dom/scripts/systemhtml.py
index 75308d4eb7cc81b256c0d77eca9b051297b3fd83..24ecbb83e2d036e760a64eac114d1cc7ef442691 100644
--- a/tools/dom/scripts/systemhtml.py
+++ b/tools/dom/scripts/systemhtml.py
@@ -618,6 +618,7 @@ class HtmlDartInterfaceGenerator(object):
     return new {0}.internal_();
   }}
 
+  @Deprecated("Internal Use Only")
   {0}.internal_() : super.internal_();
 
 '''.format(class_name)
@@ -632,6 +633,7 @@ class HtmlDartInterfaceGenerator(object):
     return new {0}.internal_();
   }}
 
+  @Deprecated("Internal Use Only")
   {0}.internal_() {{ }}
 
 {1}'''.format(class_name, js_interop_equivalence_op)