Snapshot child refs shouldn't lose information.

Author: FrankSalad

lib/modules/database/snapshot.js

@@ -42,11 +42,14 @@ export default class Snapshot {
 
   child(path: string) {
     const value = deepGet(this.value, path);
+    const exportValue = deepGet(this.exportValue, path);
     const childRef = this.ref.child(path);
     return new Snapshot(childRef, {
       value,
+      exportValue,
       key: childRef.key,
       exists: value !== null,
+      priority: (exportValue && Object.prototype.hasOwnProperty.call(exportValue, '.priority')) ? exportValue['.priority'] : undefined,
       childKeys: isObject(value) ? Object.keys(value) : [],
     });
   }