Wrap the GCache Contents content in a details element.

Bug: 896123
Change-Id: I0bb79920cea7aa6a8223d226efdfda2b3fd903eb
Reviewed-on: https://chromium-review.googlesource.com/c/1350437Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610766}

chrome/browser/resources/chromeos/drive_internals.css

@@ -25,3 +25,12 @@
 
 .log-info {
 }
+
+summary {
+  font-size: 1.5em;
+}
+
+summary h2 {
+  display: inline;
+  font-size: inherit;
+}

chrome/browser/resources/chromeos/drive_internals.html

@@ -136,7 +136,8 @@
     </section>
 
     <section id="gcache-contents-section" hidden>
-      <h2>GCache Contents</h2>
+      <details>
+        <summary><h2>GCache Contents</h2></summary>
         <table>
           <tbody id="gcache-contents">
             <tr>
@@ -147,6 +148,7 @@
             </tr>
           </tbody>
         </table>
+      </details>
       <ul>
         <li>
           Total Size: