Handle service worker errors and update the fallback algorithm

Author: meacer

fetch.bs

@@ -3300,26 +3300,22 @@ steps:
 
 <h4 id=https-upgrades-fallback>Fallback algorithm</h4>
 
-<p>Runs after the Upgrade algorithm. This algorithm determines whether the upgraded
-request completed without a network error. If not, it retries the request over <code>"http"</code>.
-
-To <dfn>handle an HTTPS upgrade fallback</dfn> given a <a for=/>request</a> <var>request</var>, run
-these steps:
+To <dfn>HTTPS upgrade fallback</dfn> given a <a for=/>request</a>
+<var>request</var> and <a for=/>response</a> <var>response</var>, run these steps:
 
 <ol>
-  <li><p>If <var>request</var>'s <code>https-upgrade</code> flag is not set, return without
-  modifying request.
-
-  <li><p>Otherwise, this is an upgraded request. Let <var>upgradedResponse</var> be the result of
-  fetching the upgraded request.
+  <li><p>If <var>request</var>'s <code>https-upgrade</code> flag is not set, the <var>request</var>
+  was not upgraded. Return <var>response</var>.
 
   <li>
-    <p>If <var>upgradedResponse</var> is a network error, initiate a fallback load by creating a
-    synthetic redirect response <var>fallbackResponse</var> that redirects to <var>request</var>'s
-    <code>https-upgrade-fallback-url</code> flag with status 307. Return
-    <var>fallbackResponse</var>.
+    <p>Otherwise, the request was upgraded.
+
+    <p>If <var>response</var> is a network error, the upgrade failed. Initiate a fallback
+    load by creating a synthetic redirect response <var>fallbackResponse</var> that redirects to
+    <var>request</var>'s <code>https-upgrade-fallback-url</code> flag with status 307.
+    Return <var>fallbackResponse</var>.
 
-  <li><p>Otherwise, the upgrade was successful. Return <var>upgradedResponse</var>.
+  <li><p>Otherwise, the upgrade was successful. Return <var>response</var>.
 </ol>
 
 <p class=note>
@@ -5266,7 +5262,8 @@ these steps:
        <var>response</var>'s <a for=response>URL list</a> has more than one item.
       </ul>
 
-      <p>then return a <a>network error</a>.
+      <p>then return the result of running <a>HTTPS upgrade fallback</a> given <var>request</var>
+       and a <a>network error</a>.
     </ol>
   </ol>
 
@@ -5333,14 +5330,16 @@ these steps:
   <a>cross-origin resource policy check</a> with <var>request</var>'s <a for=request>origin</a>,
   <var>request</var>'s <a for=request>client</a>, <var>request</var>'s
   <a for=request>destination</a>, and <var>internalResponse</var> returns <b>blocked</b>, then
-  return a <a>network error</a>.
+  return the result of running <a>HTTPS upgrade fallback</a> given <var>request</var>
+  and a <a>network error</a>.
 
   <p class=note>The <a>cross-origin resource policy check</a> runs for responses coming from the
   network and responses coming from the service worker. This is different from the
   <a>CORS check</a>, as <var>request</var>'s <a for=request>client</a> and the service worker can
   have different embedder policies.
 
- <li><p>Run <a>handle an HTTPS upgrade fallback</a> algorithm on <var>request</var>, if appropriate.</a>
+ <li>Set <var>response</var> and <var>internalResponse</var> to the result of running
+  <a>HTTPS upgrade fallback</a> given <var>request</var> and <var>response</var>.
 
  <li>
   <p>If <var>internalResponse</var>'s <a for=response>status</a> is a <a>redirect status</a>: