Fix draw order of popup annotations.

Bug: chromium:765375
Change-Id: Ifdbd33ca92ec7105778788f891095eaf280c18cf
Reviewed-on: https://pdfium-review.googlesource.com/14370
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_baannot.h b/fpdfsdk/cpdfsdk_baannot.h
index 1d71585..c7300c4 100644
--- a/fpdfsdk/cpdfsdk_baannot.h
+++ b/fpdfsdk/cpdfsdk_baannot.h
@@ -92,6 +92,8 @@
 
   void SetOpenState(bool bState);
 
+  int GetLayoutOrder() const override;
+
  protected:
   CFX_UnownedPtr<CPDF_Annot> const m_pAnnot;
 };