Fix #41: make createAttribute() lowercase the input in HTML documents

Closes: #74, #75.

Author: foolip

dom.bs

@@ -12,7 +12,7 @@ No Editor: true
 Logo: https://resources.whatwg.org/logo-dom.svg
 Abstract: DOM defines a platform-neutral model for events and node trees.
 Ignored Terms: EmptyString, Array, Elements, Document
-Boilerplate: omit conformance
+Boilerplate: omit conformance, omit feedback-header
 </pre>
 
 <!--
@@ -4670,13 +4670,13 @@ method, when invoked, must run these steps:
  production in XML, <a>throw</a> an
  {{InvalidCharacterError}} exception.
 
+ <li>If the <a>context object</a> is an <a>HTML document</a>, let
+ <var>localName</var> be <a>converted to ASCII lowercase</a>.
+
  <li>Return a new <a>attribute</a> whose
  <a for=Attr>local name</a> is <var>localName</var>.
 </ol>
 
-<p class="note no-backref">This method does not have its input
-<a>converted to ASCII lowercase</a>.
-
 The
 <dfn method for="Document">createAttributeNS(<var>namespace</var>, <var>name</var>)</dfn>
 method, when invoked, must run these steps:

dom.html

@@ -69,7 +69,7 @@
   <div class="head">
    <p data-fill-with="logo"><a class="logo" href="https://whatwg.org/"> <img alt="WHATWG" height="100" src="https://resources.whatwg.org/logo-dom.svg"> </a> </p>
    <h1 class="p-name no-ref allcaps" id="title">DOM</h1>
-   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Living Standard — Last Updated <time class="dt-updated" datetime="2015-09-16">16 September 2015</time></span></h2>
+   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Living Standard — Last Updated <time class="dt-updated" datetime="2015-09-22">22 September 2015</time></span></h2>
    <div data-fill-with="spec-metadata">
     <dl>
      <dt>Participate:
@@ -2435,9 +2435,9 @@ <h3 class="heading settled" data-level="4.5" id="interface-document"><span class
    <p>The <dfn class="idl-code" data-dfn-for="Document" data-dfn-type="method" data-export="" id="dom-document-createattribute">createAttribute(<var>localName</var>)<a class="self-link" href="#dom-document-createattribute"></a></dfn> method, when invoked, must run these steps:</p>
    <ol>
     <li>If <var>localName</var> does not match the <code><a class="css" data-link-type="type" href="http://www.w3.org/TR/xml/#NT-Name">Name</a></code> production in XML, <a data-link-type="dfn" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> an <code class="idl"><a data-link-type="idl" href="https://heycam.github.io/webidl/#invalidcharactererror">InvalidCharacterError</a></code> exception. 
+    <li>If the <a data-link-type="dfn" href="#context-object">context object</a> is an <a data-link-type="dfn" href="#html-document">HTML document</a>, let <var>localName</var> be <a data-link-type="dfn" href="#converted-to-ascii-lowercase">converted to ASCII lowercase</a>. 
     <li>Return a new <a data-link-type="dfn" href="#concept-attribute">attribute</a> whose <a data-link-type="dfn" href="#concept-attribute-local-name">local name</a> is <var>localName</var>. 
    </ol>
-   <p class="note no-backref" role="note">This method does not have its input <a data-link-type="dfn" href="#converted-to-ascii-lowercase">converted to ASCII lowercase</a>. </p>
    <p>The <dfn class="idl-code" data-dfn-for="Document" data-dfn-type="method" data-export="" id="dom-document-createattributens">createAttributeNS(<var>namespace</var>, <var>name</var>)<a class="self-link" href="#dom-document-createattributens"></a></dfn> method, when invoked, must run these steps:</p>
    <ol>
     <li>Let <var>namespace</var>, <var>prefix</var>, <var>localName</var>, and <var>name</var> be the result of passing <var>namespace</var> and <var>name</var> to <a data-link-type="dfn" href="#validate-and-extract">validate and extract</a>. Rethrow any exceptions. 
@@ -3130,7 +3130,7 @@ <h3 class="heading settled" data-level="5.1" id="introduction-to-dom-ranges"><sp
      <code class="idl"><a data-link-type="idl" href="#element">Element</a></code>: <code>p</code> 
      <ul>
       <li class="t1"><code class="idl"><a data-link-type="idl" href="#element">Element</a></code>: <code class="lang-markup highlight"><span class="nt">&lt;img</span> <span class="na">src=</span><span class="s">"insanity-wolf"</span> <span class="na">alt=</span><span class="s">"Little-ending BOM; decode as big-endian!"</span><span class="nt">></span></code> 
-      <li class="t3"><code class="idl"><a data-link-type="idl" href="#text">Text</a></code>: <span> CSS 2.1 syndata is </span> 
+      <li class="t3"><code class="idl"><a data-link-type="idl" href="#text">Text</a></code>: <span> CSS 2.1 syndata is </span> 
       <li class="t1">
        <code class="idl"><a data-link-type="idl" href="#element">Element</a></code>: <code class="lang-markup highlight"><span class="nt">&lt;em></span></code> 
        <ul>