Clean up bookmark related codes.

core/src/fpdfdoc/doc_bookmark.cpp

Index: core/src/fpdfdoc/doc_bookmark.cpp
diff --git a/core/src/fpdfdoc/doc_bookmark.cpp b/core/src/fpdfdoc/doc_bookmark.cpp
index 0ae649ecdd113381d157c01ffa42559836194a36..e7b383eced7201b6ffd5fb1374fe21c5bd1adca7 100644
--- a/core/src/fpdfdoc/doc_bookmark.cpp
+++ b/core/src/fpdfdoc/doc_bookmark.cpp
@@ -5,32 +5,32 @@
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../include/fpdfdoc/fpdf_doc.h"
-CPDF_Bookmark CPDF_BookmarkTree::GetFirstChild(CPDF_Bookmark Parent)
+CPDF_Bookmark CPDF_BookmarkTree::GetFirstChild(const CPDF_Bookmark& parent) const
 {
-    if (Parent.m_pDict == NULL) {
+    if (!parent.m_pDict) {
         CPDF_Dictionary* pRoot = m_pDocument->GetRoot()->GetDict("Outlines");
-        if (pRoot == NULL) {
-            return NULL;
+        if (!pRoot) {
+            return CPDF_Bookmark();
         }
-        return pRoot->GetDict("First");
+        return CPDF_Bookmark(pRoot->GetDict("First"));
     }
-    return Parent.m_pDict->GetDict("First");
+    return CPDF_Bookmark(parent.m_pDict->GetDict("First"));
 }
-CPDF_Bookmark CPDF_BookmarkTree::GetNextSibling(CPDF_Bookmark This)
+CPDF_Bookmark CPDF_BookmarkTree::GetNextSibling(const CPDF_Bookmark& bookmark) const
 {
-    if (This.m_pDict == NULL) {
-        return NULL;
+    if (!bookmark.m_pDict) {
+        return CPDF_Bookmark();
     }
-    CPDF_Dictionary *pNext = This.m_pDict->GetDict("Next");
-    return pNext == This.m_pDict ? NULL : pNext;
+    CPDF_Dictionary *pNext = bookmark.m_pDict->GetDict("Next");
+    return pNext == bookmark.m_pDict ? CPDF_Bookmark() : CPDF_Bookmark(pNext);
 }
-FX_DWORD CPDF_Bookmark::GetColorRef()
+FX_DWORD CPDF_Bookmark::GetColorRef() const
 {
     if (!m_pDict) {
         return 0;
     }
     CPDF_Array* pColor = m_pDict->GetArray("C");
-    if (pColor == NULL) {
+    if (!pColor) {
         return FXSYS_RGB(0, 0, 0);
     }
     int r = FXSYS_round(pColor->GetNumber(0) * 255);
@@ -38,39 +38,40 @@ FX_DWORD CPDF_Bookmark::GetColorRef()
     int b = FXSYS_round(pColor->GetNumber(2) * 255);
     return FXSYS_RGB(r, g, b);
 }
-FX_DWORD CPDF_Bookmark::GetFontStyle()
+FX_DWORD CPDF_Bookmark::GetFontStyle() const
 {
     if (!m_pDict) {
         return 0;
     }
     return m_pDict->GetInteger("F");
 }
-CFX_WideString CPDF_Bookmark::GetTitle()
+CFX_WideString CPDF_Bookmark::GetTitle() const
 {
     if (!m_pDict) {
         return CFX_WideString();
     }
     CPDF_String* pString = (CPDF_String*)m_pDict->GetElementValue("Title");
-    if (pString == NULL || pString->GetType() != PDFOBJ_STRING) {
+    if (!pString || pString->GetType() != PDFOBJ_STRING) {
         return CFX_WideString();
     }
     CFX_WideString title = pString->GetUnicodeText();
     FX_LPWSTR buf = title.LockBuffer();
-    int len = title.GetLength(), i;
-    for (i = 0; i < len; i ++)
+    int len = title.GetLength();
+    for (int i = 0; i < len; i++) {
         if (buf[i] < 0x20) {
             buf[i] = 0x20;
         }
+    }
     title.ReleaseBuffer(len);
     return title;
 }
-CPDF_Dest CPDF_Bookmark::GetDest(CPDF_Document* pDocument)
+CPDF_Dest CPDF_Bookmark::GetDest(CPDF_Document* pDocument) const
 {
     if (!m_pDict) {
         return NULL;
     }
     CPDF_Object* pDest = m_pDict->GetElementValue("Dest");
-    if (pDest == NULL) {
+    if (!pDest) {
         return NULL;
     }
     if (pDest->GetType() == PDFOBJ_STRING || pDest->GetType() == PDFOBJ_NAME) {
@@ -82,7 +83,7 @@ CPDF_Dest CPDF_Bookmark::GetDest(CPDF_Document* pDocument)
     }
     return NULL;
 }
-CPDF_Action CPDF_Bookmark::GetAction()
+CPDF_Action CPDF_Bookmark::GetAction() const
 {
     if (!m_pDict) {
         return NULL;