Add an Unstable comment/annotation on caretRangeFromPoint

tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate

 // Copyright (c) 2012, 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.
 
 // WARNING: Do not edit - generated code.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 $!MEMBERS
 
 $if DART2JS
   @DomName('Document.body')
   BodyElement body;
 $else
   @DomName('Document.body')
   BodyElement get body => _body;
 
   @DomName('Document.body')
   set body(BodyElement value) {
     _body = value;
   }
 $endif
 
+  /// UNSTABLE: Chrome-only - create a Range from the given point.
   @DomName('Document.caretRangeFromPoint')
+  @Unstable()
   Range caretRangeFromPoint(int x, int y) {
     return _caretRangeFromPoint(x, y);
   }
 
   @DomName('Document.elementFromPoint')
   Element elementFromPoint(int x, int y) {
     return _elementFromPoint(x, y);
   }
 
   /**
@@ skipping 521 matching lines @@
   /// parameter must be provided.
   @Experimental()
   ElementUpgrader createElementUpgrader(Type type, {String extendsTag}) {
 $if DART2JS
     return new _JSElementUpgrader(this, type, extendsTag);
 $else
     return new _VMElementUpgrader(this, type, extendsTag);
 $endif
   }
 }