src/vs/workbench/services/editor/browser/editorService.ts/EditorService/handleActiveEditorChange
class EditorService:	private handleActiveEditorChange(group: IEditorGroup): void {
		if (group !== this.editorGroupService.activeGroup) {
			return; // ignore if not the active group
		}

		if (!this.lastActiveEditor && !group.activeEditor) {
			return; // ignore if we still have no active editor
		}

		this.doHandleActiveEditorChangeEvent();
	}