Create RelayMutationQueue

Summary: This is part 2 of contextualizing `RelayMutationTransaction`. D2632150 moved some state into a class, but left the mutation queue and associated maps global. Changes include:

- Create `RelayMutationQueue` to manage the queue of mutations for a given Relay context.
- Move most queue management logic from MutationTransaction to MutationQueue so that individual transactions are no longer managing the queue.
- Turn `RelayMutationTransaction` into a thin wrapper object designed for use as a public API (`RelayStore.update` could eventually return these instances)

Note that the API of `RelayMutationQueue` requires an opaque `id` input for all public methods, and this id is only known to `RelayMutationTransaction` instances created via `queue.createTransaction`.

Reviewed By: yungsters

Differential Revision: D2645472

fb-gh-sync-id: 3d71e17d7295657974fdca86f453f0e8501c79db

src/container/RelayContainer.js

@@ -341,17 +341,19 @@ function createContainerComponent(
      * Returns the pending mutation transactions affecting the given record.
      */
     getPendingTransactions(record: Object): ?Array<RelayMutationTransaction> {
-      var dataID = GraphQLStoreDataHandler.getID(record);
+      const dataID = GraphQLStoreDataHandler.getID(record);
       invariant(
         dataID != null,
         'RelayContainer.getPendingTransactions(): Expected a record in `%s`.',
         componentName
       );
-      var mutationIDs = storeData.getQueuedStore().getClientMutationIDs(dataID);
+      const mutationIDs =
+        storeData.getQueuedStore().getClientMutationIDs(dataID);
       if (!mutationIDs) {
         return null;
       }
-      return mutationIDs.map(RelayMutationTransaction.get);
+      const mutationQueue = storeData.getMutationQueue();
+      return mutationIDs.map(id => mutationQueue.getTransaction(id));
     }
 
     /**