Tasks represent individual changes to the datastore that alter the local cache and need to be synced back to the server.

To create a new task, subclass Task and implement the following methods:

• performLocal: Return a Promise that does work immediately. Must resolve or the task will be thrown out. Generally, you should optimistically update the local cache here.
• performRemote: Do work that requires dependencies to have resolved and may need to be tried multiple times to succeed in case of network issues. performRemote must return a Promise, and it should always resolve with Task.Status.Finished or Task.Status.Retry. Rejections are considered exception cases and are logged to our server. Returning Task.Status.Retry will cause the TaskQueue to leave your task on the queue and run it again later. You should only return Task.Status.Retry if your task encountered a transient error (for example, a 0 but not a 400).
• shouldWaitForTask: Tasks may be arbitrarily dependent on other tasks. To ensure that performRemote is called at the right time, subclasses should implement shouldWaitForTask(other). For example, the SendDraft task is dependent on the draft's files' UploadFile tasks completing.

Tasks may also implement shouldDequeueOtherTask(other). Returning true will cause the other event to be removed from the queue. This is useful in offline mode especially, when the user might Save,Save,Save,Save,Send. Each newly queued Save can cancel the (unstarted) save task in the queue.

Tasks that need to support undo/redo should implement canBeUndone, isUndo, createUndoTask, and createIdenticalTask.