Fix a bug with limitToLast and cursors (#3668)

* Feedback.

* One more test

Author: wu-hui

firebase-firestore/src/androidTest/java/com/google/firebase/firestore/QueryTest.java

@@ -156,6 +156,50 @@ public void testListenUnlistenRelistenSequenceOfMirrorQueries() {
     assertEquals(asList(map("k", "e", "sort", -1L), map("k", "a", "sort", -2L)), data);
   }
 
+  @Test
+  public void testLimitToLastQueriesWithCursors() {
+    CollectionReference collection =
+        testCollectionWithDocs(
+            map(
+                "a", map("k", "a", "sort", 0),
+                "b", map("k", "b", "sort", 1),
+                "c", map("k", "c", "sort", 1),
+                "d", map("k", "d", "sort", 2)));
+
+    Query query = collection.limitToLast(3).orderBy("sort").endBefore(2);
+    QuerySnapshot set = waitFor(query.get());
+    List<Map<String, Object>> data = querySnapshotToValues(set);
+    assertEquals(
+        asList(map("k", "a", "sort", 0L), map("k", "b", "sort", 1L), map("k", "c", "sort", 1L)),
+        data);
+
+    query = collection.limitToLast(3).orderBy("sort").endAt(1);
+    set = waitFor(query.get());
+    data = querySnapshotToValues(set);
+    assertEquals(
+        asList(map("k", "a", "sort", 0L), map("k", "b", "sort", 1L), map("k", "c", "sort", 1L)),
+        data);
+
+    query = collection.limitToLast(3).orderBy("sort").startAt(2);
+    set = waitFor(query.get());
+    data = querySnapshotToValues(set);
+    assertEquals(asList(map("k", "d", "sort", 2L)), data);
+
+    query = collection.limitToLast(3).orderBy("sort").startAfter(0);
+    set = waitFor(query.get());
+    data = querySnapshotToValues(set);
+    assertEquals(
+        asList(map("k", "b", "sort", 1L), map("k", "c", "sort", 1L), map("k", "d", "sort", 2L)),
+        data);
+
+    query = collection.limitToLast(3).orderBy("sort").startAfter(-1);
+    set = waitFor(query.get());
+    data = querySnapshotToValues(set);
+    assertEquals(
+        asList(map("k", "b", "sort", 1L), map("k", "c", "sort", 1L), map("k", "d", "sort", 2L)),
+        data);
+  }
+
   @Test
   public void testKeyOrderIsDescendingForDescendingInequality() {
     CollectionReference collection =

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

@@ -497,11 +497,11 @@ public Target toTarget() {
         // We need to swap the cursors to match the now-flipped query ordering.
         Bound newStartAt =
             this.endAt != null
-                ? new Bound(this.endAt.getPosition(), !this.endAt.isInclusive())
+                ? new Bound(this.endAt.getPosition(), this.endAt.isInclusive())
                 : null;
         Bound newEndAt =
             this.startAt != null
-                ? new Bound(this.startAt.getPosition(), !this.startAt.isInclusive())
+                ? new Bound(this.startAt.getPosition(), this.startAt.isInclusive())
                 : null;
 
         this.memoizedTarget =