Close a page after creating it

FPDFPage_New creates a FPDF_PAGE object and adds a page to the FPDF_DOCUMENT.
However, the FPDF_PAGE object needs to be deleted by calling FPDF_ClosePage.

Bug: 807953
Change-Id: Ib0d7ca46979f855c38a03cf114c20505d825e620
Reviewed-on: https://chromium-review.googlesource.com/897930Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534057}

pdf/pdfium/pdfium_engine.cc

@@ -2885,7 +2885,10 @@ void PDFiumEngine::AppendBlankPages(int num_pages) {
         ConvertUnitDouble(page_rect.width(), kPixelsPerInch, kPointsPerInch);
     double height_in_points =
         ConvertUnitDouble(page_rect.height(), kPixelsPerInch, kPointsPerInch);
-    FPDFPage_New(doc_, i, width_in_points, height_in_points);
+    // Add a new page to the document, but delete the FPDF_PAGE object.
+    FPDF_PAGE temp_page =
+        FPDFPage_New(doc_, i, width_in_points, height_in_points);
+    FPDF_ClosePage(temp_page);
     pages_.push_back(std::make_unique<PDFiumPage>(this, i, page_rect, true));
   }