Return empty on "do not run" for running a script

Previously, as of ad3dda5, the
algorithm returned NormalCompletion(undefined) when the script was not
run.

But the service worker script will need to distinguish between when the
script was run vs. not, for deciding whether it can proceed with
installation. The counterpart service worker spec change is:
w3c/ServiceWorker#1346.

source

@@ -81986,8 +81986,9 @@ interface <dfn>Location</dfn> { // but see also <a href="#the-location-interface
        <li><p>Let <var>evaluationStatus</var> be the result of <span data-x="run a classic
        script">running the classic script</span> <var>script</var>.</p></li>
 
-       <li><p>Let <var>result</var> be undefined if <var>evaluationStatus</var> is an <span>abrupt
-       completion</span>, or <var>evaluationStatus</var>.[[Value]] otherwise.</p></li>
+       <li><p>Let <var>result</var> be undefined if <var>evaluationStatus</var> is an
+       <span>abrupt completion</span> or <var>evaluationStatus</var>.[[Value]] is
+       empty, or <var>evaluationStatus</var>.[[Value]] otherwise.</p></li>
 
        <li><p>Let <var>response</var> be null.</p></li>
 
@@ -87381,7 +87382,7 @@ interface <dfn>ApplicationCache</dfn> : <span>EventTarget</span> {
    <li><p>Let <var>settings</var> be the <span>settings object</span> of <var>script</var>.</p></li>
 
    <li><p><span>Check if we can run script</span> with <var>settings</var>. If this returns "do
-   not run" then return <span>NormalCompletion</span>(undefined).</p></li>
+   not run" then return <span>NormalCompletion</span>(empty).</p></li>
 
    <li><p><span>Prepare to run script</span> given <var>settings</var>.</p></li>
 
@@ -87444,13 +87445,8 @@ interface <dfn>ApplicationCache</dfn> : <span>EventTarget</span> {
 
    <li><p><span>Clean up after running script</span> with <var>settings</var>.</p></li>
 
-   <li>
-    <p>If <var>evaluationStatus</var> is a normal completion, return
-    <var>evaluationStatus</var>.</p>
-
-    <p class="note">This value is only ever used by the <span data-x="javascript
-    protocol"><code>javascript:</code> URL steps</span>.</p>
-   </li>
+   <li><p>If <var>evaluationStatus</var> is a normal completion, then return
+   <var>evaluationStatus</var>.</p></li>
 
    <li><p>If we've reached this point, <var>evaluationStatus</var> was left as null because the
    script was <span data-x="abort a running script">aborted prematurely</span> during evaluation.
@@ -87468,7 +87464,7 @@ interface <dfn>ApplicationCache</dfn> : <span>EventTarget</span> {
    <li><p>Let <var>settings</var> be the <span>settings object</span> of <var>script</var>.</p></li>
 
    <li><p><span>Check if we can run script</span> with <var>settings</var>. If this returns "do
-   not run" then return <span>NormalCompletion</span>(undefined).</p></li>
+   not run" then return <span>NormalCompletion</span>(empty).</p></li>
 
    <li><p><span>Prepare to run script</span> given <var>settings</var>.</p></li>