SQLiteRemoteDocumentCache.java: implement equals() and hashCode() in BackfillKey

Author: dconeybe

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

@@ -44,6 +44,7 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
@@ -488,6 +489,25 @@ private static class BackfillKey {
         this.readTimeNanos = readTimeNanos;
       }
 
+      @Override
+      public boolean equals(Object object) {
+        if (object == this) {
+          return true;
+        }
+        if (!(object instanceof BackfillKey)) {
+          return false;
+        }
+        BackfillKey other = (BackfillKey) object;
+        return readTimeSeconds == other.readTimeSeconds
+            && readTimeNanos == other.readTimeNanos
+            && Objects.equals(path, other.path);
+      }
+
+      @Override
+      public int hashCode() {
+        return Objects.hash(path, readTimeSeconds, readTimeNanos);
+      }
+
       @NonNull
       @Override
       public String toString() {