[object-stats] Visualizer: Add mime type for unzipping

Tbr: ulan@chromium.org
No-try: true
Bug: v8:7266
Change-Id: I84195b61d3f47cf2152cf68c2dc17a391c7ffec7
Reviewed-on: https://chromium-review.googlesource.com/889058Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50892}

tools/heap-stats/trace-file-reader.js

@@ -52,7 +52,7 @@ class TraceFileReader extends HTMLElement {
 
     const reader = new FileReader();
 
-    if (file.type === 'application/gzip') {
+    if (['application/gzip', 'application/x-gzip'].includes(file.type)) {
       reader.onload = (e) => {
         try {
           const textResult = pako.inflate(e.target.result, {to: 'string'});