[pdf] Reset defer_page_unload to original value.

pdf/pdfium/pdfium_engine.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
 #include <set>
 
+#include "base/auto_reset.h"
 #include "base/i18n/encoding_detection.h"
 #include "base/i18n/icu_string_conversions.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
@@ skipping 2438 matching lines @@
 }
 
 int PDFiumEngine::GetMostVisiblePage() {
   if (in_flight_visible_page_)
     return *in_flight_visible_page_;
 
   // We can call GetMostVisiblePage through a callback from PDFium. We have
   // to defer the page deletion otherwise we could potentially delete the page
   // that originated the calling JS request and destroy the objects that are
   // currently being used.
-  defer_page_unload_ = true;
+  base::AutoReset<bool> defer_page_unload_guard(&defer_page_unload_, true);
   CalculateVisiblePages();
-  defer_page_unload_ = false;
   return most_visible_page_;
 }
 
 pp::Rect PDFiumEngine::GetPageRect(int index) {
   pp::Rect rc(pages_[index]->rect());
   rc.Inset(-kPageShadowLeft, -kPageShadowTop,
            -kPageShadowRight, -kPageShadowBottom);
   return rc;
 }
 
@@ skipping 1673 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf