many changes related to #1192:

- use CSS contain wherever possible to reduce subtrees of forced reflows
- reduced dependency between note and note_contents updates which will reduce number of updates to components
- optimization of "many rows" querying

src/public/app/services/load_results.js

@@ -120,4 +120,11 @@ export default class LoadResults {
             && this.contentNoteIdToSourceId.length === 0
             && this.options.length === 0;
     }
+
+    isEmptyForTree() {
+        return Object.keys(this.noteIdToSourceId).length === 0
+            && this.branches.length === 0
+            && this.attributes.length === 0
+            && this.noteReorderings.length === 0;
+    }
 }