Start backend query processing before local cache processing (#3422)

Author: schmidt-sebastian

firebase-firestore/CHANGELOG.md

@@ -8,6 +8,8 @@ by opting into a release at
   AppCheck users that set their expiration time to under an hour.
 - [fixed] Fixed a potential problem during Firestore's shutdown that prevented 
   the shutdown from proceeding if a network connection was opened right before.
+- [changed] Queries are now send to the backend before the SDK starts local 
+  processing, which reduces overall Query latency.
 
 # 24.0.1
 - [changed] Improved performance for databases that contain many document

firebase-firestore/src/main/java/com/google/firebase/firestore/core/SyncEngine.java

@@ -201,10 +201,11 @@ public int listen(Query query) {
     hardAssert(!queryViewsByQuery.containsKey(query), "We already listen to query: %s", query);
 
     TargetData targetData = localStore.allocateTarget(query.toTarget());
+    remoteStore.listen(targetData);
+
     ViewSnapshot viewSnapshot = initializeViewAndComputeSnapshot(query, targetData.getTargetId());
     syncEngineListener.onViewSnapshots(Collections.singletonList(viewSnapshot));
 
-    remoteStore.listen(targetData);
     return targetData.getTargetId();
   }