Clarify the error handling for Location#{assign,replace}.

source

@@ -80072,32 +80072,65 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
   <code>Document</code> object's <span>browsing context</span>'s <span>active document</span>.</p>
 
   <p>When the <dfn><code data-x="dom-location-assign">assign(<var>url</var>)</code></dfn>
-  method is invoked, the UA must <span data-x="resolve a url">resolve</span> the argument, relative
-  to the <span>API base URL</span> specified by the <span>entry settings object</span>, and if that
-  is successful, must <span>navigate</span><!--DONAV location.href/assign--> the <span>browsing
-  context</span> to the specified <var>url</var>, with <span>exceptions enabled</span>. If
-  the <span>browsing context</span>'s <span>session history</span> contains only one
-  <code>Document</code>, and that was the <code>about:blank</code> <code>Document</code> created
-  when the <span>browsing context</span> was created, then the navigation must be done with
-  <span>replacement enabled</span>.</p> <!-- READ ME WHEN EDITING THIS: IE and Firefox only seem to
-  treat it that way if the DOM is still a virgin DOM; Safari doesn't check that. Thus this might
-  need changing if testing shows the IE/Firefox behaviour is required here. -->
-
-  <p>When the <dfn><code data-x="dom-location-replace">replace(<var>url</var>)</code></dfn> method is invoked, the UA must <span data-x="resolve a
-  url">resolve</span> the argument, relative to the <span>API base URL</span> specified by the
-  <span>entry settings object</span>, and if that is successful, <span>navigate</span><!--DONAV
-  location.href/replace--> the <span>browsing context</span> to the specified <var>url</var> with <span>replacement enabled</span> and <span>exceptions enabled</span>.</p>
+  method is invoked, the user agent must run the following steps:
+
+  <ol>
+
+   <li>
+
+    <p><span data-x="resolve a url">Resolve</span> <var>url</var>, relative to the
+    <span>API base URL</span> specified by the <span>entry settings object</span> and let
+    <var>parsedURL</var> be the <span>resulting parsed URL</span>.</p>
+
+    <p>If this is not successful, throw a <code>SyntaxError</code> exception and abort these
+    steps.</p>
+
+   </li>
+
+   <li>
+
+    <p><span>Navigate</span><!--DONAV location.href/assign--> the <span>browsing context</span> to
+    <var>parsedURL</var>, with <span>exceptions enabled</span>.</p>
+
+    <p>If the <span>browsing context</span>'s <span>session history</span> contains only one
+    <code>Document</code>, and that was the <code>about:blank</code> <code>Document</code> created
+    when the <span>browsing context</span> was created, then the navigation must be done with
+    <span>replacement enabled</span>.</p>
+    <!-- READ ME WHEN EDITING THIS: IE and Firefox only seem to treat it that way if the DOM is
+         still a virgin DOM; Safari doesn't check that. Thus this might need changing if testing
+         shows the IE/Firefox behaviour is required here. -->
+
+   </li>
+
+  </ol>
+
+  <p>When the <dfn><code data-x="dom-location-replace">replace(<var>url</var>)</code></dfn>
+  method is invoked, the user agent must run the following steps:
+
+  <ol>
+
+   <li>
+
+    <p><span data-x="resolve a url">Resolve</span> <var>url</var>, relative to the
+    <span>API base URL</span> specified by the <span>entry settings object</span> and let
+    <var>parsedURL</var> be the <span>resulting parsed URL</span>.</p>
+
+    <p>If this is not successful, throw a <code>SyntaxError</code> exception and abort these
+    steps.</p>
+
+   </li>
+
+   <li><p><span>Navigate</span><!--DONAV location.href/replace--> the
+   <span>browsing context</span> to <var>parsedURL</var>, with <span>replacement enabled</span>
+   and <span>exceptions enabled</span>.</p></li>
+
+  </ol>
 
   <p>Navigation for the <code data-x="dom-location-assign">assign()</code> and <code
   data-x="dom-location-replace">replace()</code> methods must be done with the <span>responsible
   browsing context</span> specified by the <span>incumbent settings object</span> as the
   <span>source browsing context</span>.</p>
 
-  <p>If the <span data-x="resolve a url">resolving</span> step of the <code
-  data-x="dom-location-assign">assign()</code> and <code
-  data-x="dom-location-replace">replace()</code> methods is not successful, then the user agent must
-  instead throw a <code>SyntaxError</code> exception.</p>
-
   <p>When the <dfn><code data-x="dom-location-reload">reload()</code></dfn> method is invoked, the
   user agent must run the appropriate steps from the following list:</p>