Bug 1952343 - [about:memory] Wait for document to regain focus before reopening the file picker; r=mccr8

Differential Revision: https://phabricator.services.mozilla.com/D241441

toolkit/components/aboutmemory/content/aboutMemory.js

@@ -327,13 +327,24 @@ window.onload = function () {
         // onchange handler to be re-called without having to go via the file
         // picker.
         if (!aElem.skipClick) {
+          // Attempts to reopen the picker immediately might fail because the
+          // focus may not have switched back on some platform, so explicitly
+          //  wait for focus here.
+          if (!this.ownerDocument.hasFocus()) {
+            let input = this;
+            this.ownerDocument.addEventListener("focus", (e) => {
+              input.click();
+            }, { once: true });
+            return;
+          }
           this.click();
         }
-      } else {
-        let filename1 = this.filename1;
-        delete this.filename1;
-        updateAboutMemoryFromTwoFiles(filename1, file.mozFullPath);
+        return;
       }
+
+      let filename1 = this.filename1;
+      delete this.filename1;
+      updateAboutMemoryFromTwoFiles(filename1, file.mozFullPath);
     }
   );