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

core/include/fpdfdoc/fpdf_doc.h

Index: core/include/fpdfdoc/fpdf_doc.h
diff --git a/core/include/fpdfdoc/fpdf_doc.h b/core/include/fpdfdoc/fpdf_doc.h
index 18dc7aa06419696e81797d84e0c23d1e5053205b..a329ac5e0868e2ace94604367a2a9a634e2a1280 100644
--- a/core/include/fpdfdoc/fpdf_doc.h
+++ b/core/include/fpdfdoc/fpdf_doc.h
@@ -31,7 +31,6 @@ class CPDF_FormNotify;
 class CPDF_IconFit;
 class CPDF_InterForm;
 class CPDF_Link;
-class CPDF_LinkList;
 class CPDF_LWinParam;
 class CPDF_Metadata;
 class CPDF_NumberTree;
@@ -357,29 +356,25 @@ class CPDF_FileSpec {
  protected:
   CPDF_Object* m_pObj;
 };
+
 class CPDF_LinkList {
  public:
-  CPDF_LinkList(CPDF_Document* pDoc) { m_pDocument = pDoc; }
-
+  CPDF_LinkList();
   ~CPDF_LinkList();
 
-  CPDF_Link GetLinkAtPoint(CPDF_Page* pPage, FX_FLOAT pdf_x, FX_FLOAT pdf_y);
-
-  int CountLinks(CPDF_Page* pPage);
-
-  CPDF_Link GetLink(CPDF_Page* pPage, int index);
-
-  CPDF_Document* GetDocument() const { return m_pDocument; }
-
- protected:
-  CPDF_Document* m_pDocument;
-
-  CFX_MapPtrToPtr m_PageMap;
+  CPDF_Link GetLinkAtPoint(CPDF_Page* pPage,
+                           FX_FLOAT pdf_x,
+                           FX_FLOAT pdf_y,
+                           int* z_order);
 
+ private:
   CFX_PtrArray* GetPageLinks(CPDF_Page* pPage);
 
   void LoadPageLinks(CPDF_Page* pPage, CFX_PtrArray* pList);
+
+  CFX_MapPtrToPtr m_PageMap;
 };
+
 class CPDF_Link {
  public:
   CPDF_Link() : m_pDict(nullptr) {}
@@ -656,7 +651,8 @@ class CPDF_InterForm : public CFX_PrivateData {
 
   CPDF_FormControl* GetControlAtPoint(CPDF_Page* pPage,
                                       FX_FLOAT pdf_x,
-                                      FX_FLOAT pdf_y) const;
+                                      FX_FLOAT pdf_y,
+                                      int* z_order) const;
 
   CPDF_FormControl* GetControlByDict(CPDF_Dictionary* pWidgetDict) const;
 
@@ -833,8 +829,6 @@ class CPDF_FormField {
 
   FX_DWORD GetFlags() { return m_Flags; }
 
-  CPDF_InterForm* GetInterForm() const { return m_pForm; }
-
   CPDF_Dictionary* GetFieldDict() const { return m_pDict; }
 
   void SetFieldDict(CPDF_Dictionary* pDict) { m_pDict = pDict; }