location.hash = "" should result in a fragment

Although some browsers currently do not add a fragment if hash is set
to the empty string, they won’t remove a fragment either when hash is
set to the empty string. Therefore aligning with Firefox makes more
sense, which consistently gives a fragment.

This makes the location API slightly inconsistent from the point of
<a>, <area>, and URL, but compatibility has to win.

Fixes #1177.

source

@@ -81047,28 +81047,23 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
    <li><p>If <var>copyURL</var>'s <span data-x="concept-url-scheme">scheme</span> is "<code
    data-x="">javascript</code>", terminate these steps.</p></li>
 
-   <li><p>If the given value is the empty string, set <var>copyURL</var>'s <span
-   data-x="concept-url-fragment">fragment</span> to null.
-
-   <li>
-    <p>Otherwise, run these substeps:</p>
-
-    <ol>
-     <li><p>Let <var>input</var> be the given value with a single leading "<code data-x="">#</code>"
-     removed, if any.</p></li>
+   <li><p>Let <var>input</var> be the given value with a single leading "<code data-x="">#</code>"
+   removed, if any.</p></li>
 
-     <li><p>Set <var>copyURL</var>'s <span data-x="concept-url-fragment">fragment</span> to the
-     empty string.</p></li>
+   <li><p>Set <var>copyURL</var>'s <span data-x="concept-url-fragment">fragment</span> to the empty
+   string.</p></li>
 
-     <li><p><span data-x="basic url parser">Basic URL parse</span> <var>input</var>, with
-     <var>copyURL</var> as <var>url</var> and <span>fragment state</span> as <var>state
-     override</var>.</p></li>
-    </ol>
-   </li>
+   <li><p><span data-x="basic url parser">Basic URL parse</span> <var>input</var>, with
+   <var>copyURL</var> as <var>url</var> and <span>fragment state</span> as <var>state
+   override</var>.</p></li>
 
    <li><p><span><code>Location</code>-object-setter navigate</span> to <var>copyURL</var>.</p></li>
   </ol>
 
+  <p class="note">Unlike the equivalent API for the <code>a</code> and <code>area</code> elements,
+  the <code data-x="dom-location-hash">hash</code> attribute's setter does not special case the
+  empty string to remain compatible with deployed scripts.</p>
+
   <hr>
 
   <p>When the <dfn><code data-x="dom-location-assign">assign(<var>url</var>)</code></dfn>