Don't throw when getting selection(Direction|Start|End) on input

third_party/WebKit/Source/core/html/HTMLInputElement.idl

 /*
  * Copyright (C) 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 61 matching lines @@
     readonly attribute boolean willValidate;
     readonly attribute ValidityState validity;
     readonly attribute DOMString validationMessage;
     boolean checkValidity();
     boolean reportValidity();
     void setCustomValidity(DOMString error);
 
     readonly attribute NodeList labels;
 
     void select();
-    [RaisesException, ImplementedAs=selectionStartForBinding] attribute unsigned long selectionStart;
-    [RaisesException, ImplementedAs=selectionEndForBinding] attribute unsigned long selectionEnd;
-    [RaisesException, ImplementedAs=selectionDirectionForBinding] attribute DOMString selectionDirection;
+    [RaisesException, ImplementedAs=selectionStartForBinding] attribute unsigned long? selectionStart;
+    [RaisesException, ImplementedAs=selectionEndForBinding] attribute unsigned long? selectionEnd;
+    [RaisesException, ImplementedAs=selectionDirectionForBinding] attribute DOMString? selectionDirection;
     [RaisesException] void setRangeText(DOMString replacement);
     [RaisesException] void setRangeText(DOMString replacement,
                                         unsigned long start,
                                         unsigned long end,
                                         optional SelectionMode selectionMode = "preserve");
     [RaisesException, ImplementedAs=setSelectionRangeForBinding]
     void setSelectionRange(unsigned long start,
                            unsigned long end,
                            optional DOMString direction);
 
     // obsolete members
     // https://html.spec.whatwg.org/#HTMLInputElement-partial
     [CEReactions, Reflect] attribute DOMString align;
     [CEReactions, Reflect] attribute DOMString useMap;
 
     // HTML autocapitalize proposal
     // https://github.com/mounirlamouri/html-autocapitalize/blob/master/proposal.md
     [Measure] attribute DOMString autocapitalize;
 
     // HTML Media Capture
     // http://www.w3.org/TR/html-media-capture/
     [RuntimeEnabled=MediaCapture, Reflect] attribute boolean capture;
 
     // Non-standard APIs
     [Reflect, MeasureAs=PrefixedDirectoryAttribute] attribute boolean webkitdirectory;
     [Reflect, MeasureAs=IncrementalAttribute] attribute boolean incremental;
 };