Make conversion between CPDF_Action and its dictionary explicit

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 60f41a55542537480757661c4a3cd4b6c7aaa1fc..dbcc7f433e08546e99f764edb36fedf1525d0699 100644
--- a/core/include/fpdfdoc/fpdf_doc.h
+++ b/core/include/fpdfdoc/fpdf_doc.h
@@ -264,17 +264,6 @@ public:
 class CPDF_Action : public CFX_Object
 {
 public:
-
-    CPDF_Action(CPDF_Dictionary* pDict = NULL)
-    {
-        m_pDict = pDict;
-    }
-
-    operator CPDF_Dictionary* () const
-    {
-        return m_pDict;
-    }
-
     enum ActionType {
         Unknown = 0,
         GoTo,
@@ -297,6 +286,13 @@ public:
         GoTo3DView
     };
 
+    CPDF_Action() : m_pDict(nullptr) { }
+    explicit CPDF_Action(CPDF_Dictionary* pDict) : m_pDict(pDict) { }
+
+    operator bool () const { return m_pDict != NULL; }
+
+    CPDF_Dictionary* GetDict() const { return m_pDict; }
+
     CFX_ByteString		GetTypeName() const
     {
         return m_pDict->GetString("S");
@@ -422,7 +418,7 @@ public:
 
     CPDF_Action			GetSubAction(FX_DWORD iIndex) const;
 
-
+protected:
     CPDF_Dictionary*	m_pDict;
 };
 class CPDF_AAction : public CFX_Object