Fix scrolling to fragments

Chrome and Safari both do a literal match first before using the decoded fragment. Edge does something very similar, though seems to differ in :target handling. Firefox would like to align per https://bugzilla.mozilla.org/show_bug.cgi?id=1380323 as our compliant behavior causes issues.

Tests: web-platform-tests/wpt#6887.

Fixes whatwg#2902.

Author: annevk

source

@@ -82873,39 +82873,47 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
   document</span> is.</p>
 
   <ol>
+   <li><p>Let <var>fragment</var> be the document's <span data-x="concept-document-url">URL</span>'s
+   <span data-x="concept-url-fragment">fragment</span>.</p></li>
 
-   <li><p>Apply the <span>URL parser</span> algorithm to the <span>URL</span>, and let <var>fragid</var> be the <span data-x="concept-url-fragment">fragment</span> component of the
-   resulting <span>URL record</span>.</p></li><!-- parsing can't fail, since we checked earlier on
-   when navigating -->
+   <li><p>If <var>fragment</var> is the empty string, then <span>the indicated part of the
+   document</span> is the top of the document; return.</p></li>
 
-   <li><p>If <var>fragid</var> is the empty string, then <span>the indicated part of the
-   document</span> is the top of the document; stop the algorithm here.</p></li>
+   <li><p>If <span>find a potential indicated element</span> with <var>fragment</var> returns
+   non-null, than the return value is <span>the indicated part of the document</span>;
+   return.</p></li>
 
-   <li><p>Let <var>fragid bytes</var> be the result of <span data-x="percent
-   decode">percent-decoding</span> <var>fragid</var>.</p></li>
+   <li><p>Let <var>fragmentBytes</var> be the result of <span data-x="percent
+   decode">percent-decoding</span> <var>fragment</var>.</p></li>
 
-   <li><p>Let <var>decoded fragid</var> be the result of running <span>UTF-8 decode without BOM or
-   fail</span> on <var>fragid bytes</var>. If <var>decoded fragid</var> is failure, jump to the step
-   labeled <i>no decoded fragid</i>.</p></li>
+   <li><p>Let <var>decodedFragment</var> be the result of running <span>UTF-8 decode without BOM or
+   fail</span> on <var>fragmentBytes</var>.</p></li>
 
-   <li><p>If there is an element <span data-x="in a document tree">in the document tree</span> that
-   has an <span data-x="concept-id">ID</span> exactly equal to <var>decoded fragid</var>, then the
-   first such element in <span>tree order</span> is <span>the indicated part of the document</span>;
-   stop the algorithm here.</p></li>
+   <li><p>If <span>find a potential indicated element</span> with <var>decodedFragment</var> returns
+   non-null, than the return value is <span>the indicated part of the document</span>;
+   return.</p></li>
 
-   <li><p><i>No decoded fragid</i>: If there is an <code>a</code> element <span data-x="in a
-   document tree">in the document tree</span> that has a <code data-x="attr-a-name">name</code>
-   attribute whose value is exactly equal to <var>fragid</var> (<em>not</em> <var>decoded
-   fragid</var>), then the first such element in <span>tree order</span> is <span>the indicated part
-   of the document</span>; stop the algorithm here.</p></li>
+   <li><p>If <var>decodedFragment</var> is an <span>ASCII case-insensitive</span> match for the
+   string <code data-x="">top</code>, then <span>the indicated part of the document</span> is the
+   top of the document; return.</p></li>
 
-   <li><p>If <var>fragid</var> is an <span>ASCII case-insensitive</span> match for the
-   string <code data-x="">top</code>, then <span>the indicated part of the document</span> is the top
-   of the document; stop the algorithm here.</p></li>
+   <li><p>There is no <span data-x="the indicated part of the document">indicated part of the
+   document</span>.</p></li>
+  </ol>
 
-   <li><p>Otherwise, there is no <span data-x="the indicated part of the document">indicated part of
-   the document</span>.</p></li>
+  <p>To <dfn>find a potential indicated element</dfn> given a string <var>fragment</var>, run these
+  steps:</p>
 
+  <ol>
+   <li><p>If there is an element <span data-x="in a document tree">in the document tree</span> that
+   has an <span data-x="concept-id">ID</span> equal to <var>fragment</var>, then return the first
+   such element in <span>tree order</span>.</p></li>
+
+   <li><p>If there is an <code>a</code> element <span data-x="in a document tree">in the document
+   tree</span> that has a <code data-x="attr-a-name">name</code> attribute whose value is equal to
+   <var>fragment</var>, then return the first such element in <span>tree order</span>.</p></li>
+
+   <li><p>Return null.</p></li>
   </ol>
 
   <p>The <span>task source</span> for the task mentioned in this section must be the <span>DOM
@@ -120276,6 +120284,7 @@ INSERT INTERFACES HERE
   Allen Wirfs-Brock,
   Alex Komoroske,
   Alex Russell,
+  Alphan Chen,
   Ami Fischman,
   Amos Jeffries,
   Anders Carlsson,