PDF: Consistently pass FPDF handles by value.

pdf/pdfium/pdfium_engine.h

 // 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.
 
 #ifndef PDF_PDFIUM_PDFIUM_ENGINE_H_
 #define PDF_PDFIUM_PDFIUM_ENGINE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 294 matching lines @@
 
   pp::Buffer_Dev PrintPagesAsRasterPDF(
       const PP_PrintPageNumberRange_Dev* page_ranges,
       uint32_t page_range_count,
       const PP_PrintSettings_Dev& print_settings);
 
   pp::Buffer_Dev PrintPagesAsPDF(const PP_PrintPageNumberRange_Dev* page_ranges,
                                  uint32_t page_range_count,
                                  const PP_PrintSettings_Dev& print_settings);
 
-  pp::Buffer_Dev GetFlattenedPrintData(const FPDF_DOCUMENT& doc);
+  pp::Buffer_Dev GetFlattenedPrintData(FPDF_DOCUMENT doc);
   void FitContentsToPrintableAreaIfRequired(
-      const FPDF_DOCUMENT& doc,
+      FPDF_DOCUMENT doc,
       const PP_PrintSettings_Dev& print_settings);
   void SaveSelectedFormForPrint();
 
   // Given a mouse event, returns which page and character location it's closest
   // to.
   PDFiumPage::Area GetCharIndex(const pp::MouseInputEvent& event,
                                 int* page_index,
                                 int* char_index,
                                 int* form_type,
                                 PDFiumPage::LinkTarget* target);
@@ skipping 470 matching lines @@
   bool GetPDFPageSizeByIndex(const void* pdf_buffer,
                              int pdf_buffer_size,
                              int page_number,
                              double* width,
                              double* height) override;
 };
 
 }  // namespace chrome_pdf
 
 #endif  // PDF_PDFIUM_PDFIUM_ENGINE_H_