Pass empty mask, not null when recalculation.

Author: wu-hui

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LocalDocumentsView.java

@@ -203,7 +203,9 @@ private void recalculateAndSaveOverlays(Map<DocumentKey, MutableDocument> docs)
     // along the way.
     for (MutationBatch batch : batches) {
       for (DocumentKey key : batch.getKeys()) {
-        FieldMask mask = batch.applyToLocalView(docs.get(key), masks.get(key));
+        FieldMask mask =
+            masks.containsKey(key) ? masks.get(key) : FieldMask.fromSet(new HashSet<>());
+        mask = batch.applyToLocalView(docs.get(key), mask);
         masks.put(key, mask);
         int batchId = batch.getBatchId();
         if (!documentsByBatchId.containsKey(batchId)) {

firebase-firestore/src/main/java/com/google/firebase/firestore/local/SQLiteSchema.java

@@ -73,7 +73,7 @@ class SQLiteSchema {
   }
 
   void runSchemaUpgrades() {
-    runSchemaUpgrades(0, VERSION);
+    runSchemaUpgrades(0);
   }
 
   void runSchemaUpgrades(int fromVersion) {
@@ -657,7 +657,9 @@ private void createDataMigrationTable() {
   }
 
   private void addPendingDataMigration(String migration) {
-    db.execSQL("INSERT OR IGNORE INTO data_migrations (migration_name) VALUES (?)", new String[] {migration});
+    db.execSQL(
+        "INSERT OR IGNORE INTO data_migrations (migration_name) VALUES (?)",
+        new String[] {migration});
   }
 
   private boolean tableExists(String table) {

firebase-firestore/src/test/java/com/google/firebase/firestore/local/SQLiteOverlayMigrationManagerTest.java

@@ -44,8 +44,6 @@
 @RunWith(RobolectricTestRunner.class)
 @Config(manifest = Config.NONE)
 public class SQLiteOverlayMigrationManagerTest {
-  private static boolean overlayEnabled;
-
   private Persistence persistence;
   private LocalStore localStore;