Remove even more const casting from core.

core/fpdfdoc/doc_form.cpp

 // 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
 
 #include <vector>
 
 #include "core/fpdfapi/fpdf_font/include/cpdf_fontencoding.h"
 #include "core/fpdfapi/fpdf_page/include/cpdf_page.h"
@@ skipping 971 matching lines @@
         continue;
       }
       if (pKid->GetStringBy("Subtype") != "Widget") {
         continue;
       }
       AddControl(pField, pKid);
     }
   }
   return pField;
 }
-CPDF_FormControl* CPDF_InterForm::AddControl(const CPDF_FormField* pField,
+CPDF_FormControl* CPDF_InterForm::AddControl(CPDF_FormField* pField,
                                              CPDF_Dictionary* pWidgetDict) {
   const auto it = m_ControlMap.find(pWidgetDict);
   if (it != m_ControlMap.end())
     return it->second;
 
-  CPDF_FormControl* pControl =
-      new CPDF_FormControl((CPDF_FormField*)pField, pWidgetDict);
+  CPDF_FormControl* pControl = new CPDF_FormControl(pField, pWidgetDict);
   m_ControlMap[pWidgetDict] = pControl;
-  ((CPDF_FormField*)pField)->m_ControlList.Add(pControl);
+  pField->m_ControlList.Add(pControl);
   return pControl;
 }
 
 CPDF_FormField* CPDF_InterForm::CheckRequiredFields(
     const std::vector<CPDF_FormField*>* fields,
     bool bIncludeOrExclude) const {
   int nCount = m_pFieldTree->m_Root.CountFields();
   for (int i = 0; i < nCount; ++i) {
     CPDF_FormField* pField = m_pFieldTree->m_Root.GetField(i);
     if (!pField)
@@ skipping 177 matching lines @@
     FDF_ImportField(pField, L"", bNotify);
   }
   if (bNotify && m_pFormNotify)
     m_pFormNotify->AfterFormImportData(this);
   return TRUE;
 }
 
 void CPDF_InterForm::SetFormNotify(IPDF_FormNotify* pNotify) {
   m_pFormNotify = pNotify;
 }