Unify some code

core/fpdfapi/parser/cpdf_linearized.cpp

+// Copyright 2016 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 "core/fpdfapi/parser/cpdf_linearized.h"
+
+#include "core/fpdfapi/parser/cpdf_array.h"
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+
+// static
+std::unique_ptr<CPDF_Linearized> CPDF_Linearized::CreateForObject(
+    std::unique_ptr<CPDF_Object, ReleaseDeleter<CPDF_Object>> pObj) {
+  if (!pObj)

[Lei Zhang, 2016/11/02 21:34:22]

You can write this as:

UniqueDictionary pDict = ToDictionary(pObj);
if (!pDict || !pDict->GetObjectFor("Linearized"))
  return nullptr;
return pdfium::WrapUnique(new CPDF_Linearized(std::move(pDict)));

[snake, 2016/11/02 22:04:29]

Done.

[snake, 2016/11/02 22:35:16]

Do not compile with 
"UniqueDictionary pDict = ToDictionary(pObj);"

[Lei Zhang, 2016/11/03 00:46:26]

Err, UniqueDictionary pDict = ToDictionary(std::move(pObj));

[snake, 2016/11/03 01:39:27]

Done.

+    return std::unique_ptr<CPDF_Linearized>();

[Lei Zhang, 2016/11/02 21:34:22]

In https://codereview.chromium.org/2453163002 we converted a bunch of these to
just nullptr. Do the same here and save some typing?

[snake, 2016/11/02 22:04:28]

Done.

+  CPDF_Dictionary* pDict = pObj->GetDict();
+  if (!pDict || !pDict->GetObjectFor("Linearized"))
+    return std::unique_ptr<CPDF_Linearized>();
+  return std::unique_ptr<CPDF_Linearized>(new CPDF_Linearized(pDict));
+}
+
+CPDF_Linearized::CPDF_Linearized(CPDF_Dictionary* pDict) {
+  m_szFileSize = pDict->GetIntegerFor("L");
+  m_dwFirstPageNo = pDict->GetIntegerFor("P");
+  m_szLastXRefOffset = pDict->GetIntegerFor("T");
+  m_PageCount = pDict->GetIntegerFor("N");
+  m_szFirstPageEndOffset = pDict->GetIntegerFor("E");
+  m_FirstPageObjNum = pDict->GetIntegerFor("O");
+  CPDF_Array* pHintStreamRange = pDict->GetArrayFor("H");
+  size_t nHintStreamSize = pHintStreamRange ? pHintStreamRange->GetCount() : 0;
+  if (nHintStreamSize == 2 || nHintStreamSize == 4) {
+    m_szHintStart = pHintStreamRange->GetIntegerAt(0);
+    m_szHintLength = pHintStreamRange->GetIntegerAt(1);
+  }
+}
+
+CPDF_Linearized::~CPDF_Linearized() {}
+
+bool CPDF_Linearized::HasHintTable() const {
+  return GetPageCount() > 1 && GetHintStart() > 0 && GetHintLength() > 0;
+}