feat(data-table): add disconnect to data source

Author: andrewseguin

src/lib/core/data-table/data-source.ts

@@ -14,4 +14,5 @@ export interface CollectionViewer {
 
 export abstract class DataSource<T> {
   abstract connect(collectionViewer: CollectionViewer): Observable<T[]>;
+  disconnect() {}
 }

src/lib/core/data-table/data-table.ts

@@ -179,6 +179,7 @@ export class CdkTable<T> implements CollectionViewer {
   ngOnDestroy() {
     this._onDestroy.next();
     this._onDestroy.complete();
+    this.dataSource.disconnect();
   }
 
   ngOnInit() {
@@ -231,6 +232,8 @@ export class CdkTable<T> implements CollectionViewer {
    */
   private _switchDataSource(dataSource: DataSource<T>) {
     this._data = [];
+
+    this.dataSource.disconnect();
     this._dataSource = dataSource;
 
     if (this._isViewInitialized) {