Run removeOldItems_() only once per session

I just discovered some flakiness locally doing --gtest_repeat on
Trash/FilesAppBrowserTest.Test/trashMoveToTrash.

this.trashDirs_ can be cleared by removeFileOrDirectory(), so we should
add an extra check and only run removeOldItems_() when the inProgress_
set exists.

Bug: 953310
Change-Id: Ie9db7ac577c473241c39cf9e8f03c75581e9d14d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2567844Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832711}

ui/file_manager/file_manager/background/js/trash.js

@@ -142,10 +142,12 @@ class Trash {
     trashDirs = await TrashDirs.getTrashDirs(entry.filesystem, config);
 
     // Check and remove old items max once per session.
-    this.removeOldItems_(trashDirs, config, Date.now()).then(() => {
-      // In-progress set is not required after removeOldItems_() runs.
-      this.inProgress_.delete(config.id);
-    });
+    if (this.inProgress_.has(config.id)) {
+      this.removeOldItems_(trashDirs, config, Date.now()).then(() => {
+        // In-progress set is not required after removeOldItems_() runs.
+        this.inProgress_.delete(config.id);
+      });
+    }
     this.trashDirs_[config.id] = trashDirs;
     return trashDirs;
   }