SkPDF fix object counting error

src/doc/SkDocument_PDF.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDocument.h"
 #include "SkPDFCanon.h"
 #include "SkPDFCatalog.h"
@@ skipping 211 matching lines @@
         offsets.push(SkToS32(stream->bytesWritten() - baseOffset));
         SkASSERT(object == catalog.getSubstituteObject(object));
         SkASSERT(catalog.getObjectNumber(object) == i + 1);
         stream->writeDecAsText(i + 1);
         stream->writeText(" 0 obj\n");  // Generation number is always 0.
         object->emitObject(stream, &catalog);
         stream->writeText("\nendobj\n");
     }
     int32_t xRefFileOffset = SkToS32(stream->bytesWritten() - baseOffset);
 
+    // Include the zeroth object in the count.
     int32_t objCount = SkToS32(offsets.count() + 1);
 
     stream->writeText("xref\n0 ");
-    stream->writeDecAsText(objCount + 1);
+    stream->writeDecAsText(objCount);
     stream->writeText("\n0000000000 65535 f \n");
     for (int i = 0; i < offsets.count(); i++) {
         SkASSERT(offsets[i] > 0);
         stream->writeBigDecAsText(offsets[i], 10);
         stream->writeText(" 00000 n \n");
     }
     emit_pdf_footer(stream, &catalog, docCatalog.get(), objCount,
                     xRefFileOffset);
 
     // The page tree has both child and parent pointers, so it creates a
@@ skipping 112 matching lines @@
 
 SkDocument* SkDocument::CreatePDF(const char path[], SkScalar dpi) {
     SkFILEWStream* stream = SkNEW_ARGS(SkFILEWStream, (path));
     if (!stream->isValid()) {
         SkDELETE(stream);
         return NULL;
     }
     auto delete_wstream = [](SkWStream* stream, bool) { SkDELETE(stream); };
     return SkNEW_ARGS(SkDocument_PDF, (stream, delete_wstream, dpi));
 }