Fix location of onDidChangeTreeData in proposal

Part of #32592

src/vs/vscode.proposed.d.ts

@@ -918,13 +918,19 @@ declare module 'vscode' {
 	//#endregion
 
 	//#region Custom Tree View Drag and Drop https://github.com/microsoft/vscode/issues/32592
-	export interface TreeViewOptions<T> {
+	/**
+	 * A data provider that provides tree data
+	 */
+	export interface TreeDataProvider<T> {
 		/**
-		 * An optional event to signal that elements or the root have changed.
+		 * An optional event to signal that an element or root has changed.
 		 * This will trigger the view to update the changed element/root and its children recursively (if shown).
 		 * To signal that root has changed, do not pass any argument or pass `undefined` or `null`.
 		 */
-		onDidChangeTreeData?: Event<T | T[] | undefined | null | void>;
+		onDidChangeTreeData2?: Event<T | T[] | undefined | null | void>;
+	}
+
+	export interface TreeViewOptions<T> {
 		/**
 		* An optional interface to implement drag and drop in the tree view.
 		*/

src/vs/workbench/api/common/extHostTreeViews.ts

@@ -253,7 +253,9 @@ class ExtHostTreeView<T> extends Disposable {
 		}
 		this.dataProvider = options.treeDataProvider;
 		this.dndController = options.dragAndDropController;
-		if (this.dataProvider.onDidChangeTreeData) {
+		if (this.dataProvider.onDidChangeTreeData2) {
+			this._register(this.dataProvider.onDidChangeTreeData2(elementOrElements => this._onDidChangeData.fire({ message: false, element: elementOrElements })));
+		} else if (this.dataProvider.onDidChangeTreeData) {
 			this._register(this.dataProvider.onDidChangeTreeData(element => this._onDidChangeData.fire({ message: false, element })));
 		}