Bug 1067568 - Intermittent test_filehandle_readonly_exceptions.html | Assertion count 4 is greater than expected (ASSERTION: We don't know anyting about this file handle?!: 'Error', file dom/filehandle/FileService.cpp, line 234); r=bent

dom/indexedDB/IDBMutableFile.cpp

@@ -321,6 +321,11 @@ IDBMutableFile::Open(FileMode aMode, ErrorResult& aError)
     return nullptr;
   }
 
+  if (mInvalidated) {
+    aError.Throw(NS_ERROR_DOM_FILEHANDLE_NOT_ALLOWED_ERR);
+    return nullptr;
+  }
+
   nsRefPtr<IDBFileHandle> fileHandle =
     IDBFileHandle::Create(aMode, FileHandleBase::NORMAL, this);
   if (!fileHandle) {