--- a/toolkit/components/extensions/ExtensionXPCShellUtils.jsm
+++ b/toolkit/components/extensions/ExtensionXPCShellUtils.jsm
@@ -642,16 +642,20 @@ var ExtensionTestUtils = {
       },
 
       QueryInterface: XPCOMUtils.generateQI([Ci.nsIDirectoryServiceProvider]),
     };
     Services.dirsvc.registerProvider(dirProvider);
 
 
     scope.registerCleanupFunction(() => {
+      // TODO: On Windows, we can't delete a folder when it contains a file
+      // which is currently open. The crash reporter opens a file in the tmp
+      // directory and gives an FD to the child. Until the child exits, it
+      // stays open...
       tmpD.remove(true);
       Services.dirsvc.unregisterProvider(dirProvider);
 
       this.currentScope = null;
     });
   },
 
   addonManagerStarted: false,