src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/activateGroup
class EditorPart:	activateGroup(group: IEditorGroupView | GroupIdentifier): IEditorGroupView {
		const groupView = this.assertGroupView(group);
		this.doSetGroupActive(groupView);

		this._onDidActivateGroup.fire(groupView);
		return groupView;
	}