Add new public APIs to find the z-order for links and widgets.

core/src/fpdfdoc/doc_formcontrol.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 "../../include/fpdfdoc/fpdf_doc.h"
 CPDF_FormControl::CPDF_FormControl(CPDF_FormField* pField,
                                    CPDF_Dictionary* pWidgetDict) {
   m_pField = pField;
   m_pWidgetDict = pWidgetDict;
   m_pForm = m_pField->m_pForm;
 }
-CFX_FloatRect CPDF_FormControl::GetRect() {
+CFX_FloatRect CPDF_FormControl::GetRect() const {
   return m_pWidgetDict->GetRect("Rect");
 }
 CFX_ByteString CPDF_FormControl::GetOnStateName() {
   ASSERT(GetType() == CPDF_FormField::CheckBox ||
          GetType() == CPDF_FormField::RadioButton);
   CFX_ByteString csOn;
   CPDF_Dictionary* pAP = m_pWidgetDict->GetDict("AP");
   if (pAP == NULL) {
     return csOn;
   }
@@ skipping 414 matching lines @@
     return NULL;
   }
   return m_pDict->GetDict(FX_BSTRC("IF"));
 }
 int CPDF_ApSettings::GetTextPosition() {
   if (m_pDict == NULL) {
     return TEXTPOS_CAPTION;
   }
   return m_pDict->GetInteger(FX_BSTRC("TP"), TEXTPOS_CAPTION);
 }