Call pp::Size::IsEmpty() instead of !pp::Size::GetArea().

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>
 
@@ skipping 2653 matching lines @@
     return true;
 
   if (!FPDFAvail_IsPageAvail(fpdf_availability_, index, &download_hints_)) {
     if (!ContainsValue(*pending, index))
       pending->push_back(index);
     return false;
   }
 
   if (index < num_pages)
     pages_[index]->set_available(true);
-  if (!default_page_size_.GetArea())
+  if (default_page_size_.IsEmpty())
     default_page_size_ = GetPageSize(index);
   return true;
 }
 
 pp::Size PDFiumEngine::GetPageSize(int index) {
   pp::Size size;
   double width_in_points = 0;
   double height_in_points = 0;
   int rv = FPDF_GetPageSizeByIndex(
       doc_, index, &width_in_points, &height_in_points);
@@ skipping 1214 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