src/vs/workbench/services/editor/browser/editorService.ts/EditorService/onEditorGroupsReady
class EditorService:	private onEditorGroupsReady(): void {

		// Register listeners to each opened group
		for (const group of this.editorGroupService.groups) {
			this.registerGroupListeners(group as IEditorGroupView);
		}

		// Fire initial set of editor events if there is an active editor
		if (this.activeEditor) {
			this.doHandleActiveEditorChangeEvent();
			this._onDidVisibleEditorsChange.fire();
		}
	}