Add observer for BAAnnots from Javascript

fpdfsdk/include/cpdfsdk_baannot.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef FPDFSDK_INCLUDE_CPDFSDK_BAANNOT_H_
 #define FPDFSDK_INCLUDE_CPDFSDK_BAANNOT_H_
 
 #include "core/fpdfdoc/include/cpdf_aaction.h"
 #include "core/fpdfdoc/include/cpdf_action.h"
 #include "core/fpdfdoc/include/cpdf_annot.h"
 #include "core/fpdfdoc/include/cpdf_defaultappearance.h"
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_string.h"
 #include "fpdfsdk/cfx_systemhandler.h"
 #include "fpdfsdk/include/cpdfsdk_annot.h"
 
 class CFX_Matrix;
 class CFX_RenderDevice;
 class CPDF_Dictionary;
 class CPDF_RenderOptions;
 class CPDFSDK_PageView;
 
 class CPDFSDK_BAAnnot : public CPDFSDK_Annot {
  public:
+  class Observer : public CPDFSDK_Annot::Observer {
+   public:
+    explicit Observer(CPDFSDK_BAAnnot** pWatchedPtr);
+    ~Observer() override;
+
+    void OnAnnotDestroyed() override;
+
+   private:
+    CPDFSDK_BAAnnot** m_pWatchedPtr;
+  };
+
   CPDFSDK_BAAnnot(CPDF_Annot* pAnnot, CPDFSDK_PageView* pPageView);
   ~CPDFSDK_BAAnnot() override;
 
   // CPDFSDK_Annot
   CPDF_Annot::Subtype GetAnnotSubtype() const override;
   void SetRect(const CFX_FloatRect& rect) override;
   CFX_FloatRect GetRect() const override;
   CPDF_Annot* GetPDFAnnot() const override;
   void Annot_OnDraw(CFX_RenderDevice* pDevice,
                     CFX_Matrix* pUser2Device,
@@ skipping 60 matching lines @@
                        const CFX_ByteString& sContents,
                        const CFX_ByteString& sAPState = "");
 
   void SetOpenState(bool bState);
 
  protected:
   CPDF_Annot* m_pAnnot;
 };
 
 #endif  // FPDFSDK_INCLUDE_CPDFSDK_BAANNOT_H_