Add observer for BAAnnots from Javascript

fpdfsdk/cpdfsdk_baannot.cpp

 // Copyright 2016 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
 
 #include "fpdfsdk/include/cpdfsdk_baannot.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_array.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_number.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_stream.h"
 #include "core/fpdfapi/fpdf_parser/include/fpdf_parser_decode.h"
 #include "fpdfsdk/include/cpdfsdk_datetime.h"
 #include "fpdfsdk/include/fsdk_mgr.h"
 
+CPDFSDK_BAAnnot::Observer::Observer(CPDFSDK_BAAnnot** pWatchedPtr)
+    : m_pWatchedPtr(pWatchedPtr) {
+  (*m_pWatchedPtr)->AddObserver(this);
+}
+
+CPDFSDK_BAAnnot::Observer::~Observer() {
+  if (m_pWatchedPtr)
+    (*m_pWatchedPtr)->RemoveObserver(this);
+}
+
+void CPDFSDK_BAAnnot::Observer::OnAnnotDestroyed() {
+  ASSERT(m_pWatchedPtr);
+  *m_pWatchedPtr = nullptr;
+  m_pWatchedPtr = nullptr;
+}
+
 CPDFSDK_BAAnnot::CPDFSDK_BAAnnot(CPDF_Annot* pAnnot,
                                  CPDFSDK_PageView* pPageView)
     : CPDFSDK_Annot(pPageView), m_pAnnot(pAnnot) {}
 
 CPDFSDK_BAAnnot::~CPDFSDK_BAAnnot() {}
 
 CPDF_Annot* CPDFSDK_BAAnnot::GetPDFAnnot() const {
   return m_pAnnot;
 }
 
@@ skipping 372 matching lines @@
                                    CPDF_RenderOptions* pOptions) {
   m_pAnnot->GetAPForm(m_pPageView->GetPDFPage(), CPDF_Annot::Normal);
   m_pAnnot->DrawAppearance(m_pPageView->GetPDFPage(), pDevice, pUser2Device,
                            CPDF_Annot::Normal, nullptr);
 }
 
 void CPDFSDK_BAAnnot::SetOpenState(bool bOpenState) {
   if (CPDF_Annot* pAnnot = m_pAnnot->GetPopupAnnot())
     pAnnot->SetOpenState(bOpenState);
 }