message: fix(devtools): fix regression that broke node expansion (rangle/angular-devtools#88)
diff: import { DevToolsNode } from 'protocol';
  -import { DataSource } from '@angular/cdk/collections';
  -import { BehaviorSubject, Observable } from 'rxjs';
  +import { CollectionViewer, DataSource } from '@angular/cdk/collections';
  +import { BehaviorSubject, merge, Observable } from 'rxjs';
  import { MatTreeFlattener } from '@angular/material/tree';
  import { FlatTreeControl } from '@angular/cdk/tree';
  import { map } from 'rxjs/operators';
  @@ -101,10 +101,11 @@ export class ComponentDataSource extends DataSource<FlatNode> {
  return newItems;
  }
  - connect(): Observable<FlatNode[]> {
  - return this._flattenedData.pipe(
  + connect(collectionViewer: CollectionViewer): Observable<FlatNode[]> {
  + const changes = [collectionViewer.viewChange, this._treeControl.expansionModel.changed, this._flattenedData];
  + return merge(...changes).pipe(
  map(() => {
  - this._expandedData.next(this.data);
  + this._expandedData.next(this._treeFlattener.expandFlattenedNodes(this.data, this._treeControl));
  return this._expandedData.value;
  })
  );
  