Use appropriate fetch destination for CSS & JSON modules

Builds on whatwg/fetch#1691.

Tests: web-platform-tests/wpt#41665.

Fixes #7233.

source

@@ -27288,6 +27288,9 @@ document.body.appendChild(wbr);</code></pre>
      <li><p><var>destination</var> is "<code data-x="">font</code>" and
      <var>mimeTypeRecord</var> is a <span>font MIME type</span>;</p></li>
 
+     <li><p><var>destination</var> is "<code data-x="">json</code>" and
+     <var>mimeTypeRecord</var> is a <span>JSON MIME type</span></p>;</li>
+
      <li><p><var>destination</var> is "<code data-x="">style</code>" and
      <var>mimeTypeRecord</var>'s <span data-x="MIME type essence">essence</span> is
      <code>text/css</code>; or</p></li>
@@ -104824,11 +104827,14 @@ document.querySelector("button").addEventListener("click", bound);
 
    <li><p>Let <var>request</var> be a new <span data-x="concept-request">request</span> whose
    <span data-x="concept-request-url">URL</span> is <var>url</var>, <span
-   data-x="concept-request-destination">destination</span> is <var>destination</var>, <span
    data-x="concept-request-mode">mode</span> is "<code data-x="">cors</code>", <span
    data-x="concept-request-referrer">referrer</span> is <var>referrer</var>, and <span
    data-x="concept-request-client">client</span> is <var>fetchClient</var>.</p></li>
 
+   <li><p>Set <var>request</var>'s <span data-x="concept-request-destination">destination</span> to
+   the result of running the <span>fetch destination from module type</span> steps given
+   <var>destination</var> and <var>moduleType</var>.</p></li>
+
    <!--
     "serviceworker" being included here is not redundant with the Service Worker spec's own
     same-origin check, because the request's mode also affects the Origin and Sec-Fetch-Mode
@@ -105243,6 +105249,20 @@ document.querySelector("button").addEventListener("click", bound);
    <li><p>Return true.</p></li>
   </ol>
 
+  <p>The <dfn>fetch destination from module type</dfn> steps, given a <span
+  data-x="concept-request-destination">destination</span> <var>defaultDestination</var> and a
+  <span>string</span> <var>moduleType</var>, are as follows:</p>
+
+  <ol>
+   <li>If <var>moduleType</var> is "<code data-x="">json</code>", then return "<code
+   data-x="">json</code>".</li>
+
+   <li>If <var>moduleType</var> is "<code data-x="">css</code>", then return "<code
+   data-x="">style</code>".</li>
+
+   <li>Return <var>defaultDestination</var>.</li>
+  </ol>
+
   <h5 id="calling-scripts">Calling scripts</h5>
 
   <p>To <dfn export>run a classic script</dfn> given a <span>classic script</span> <var>script</var>