SkPDF: add `final` keyword to leaf classes

src/pdf/SkPDFMetadata.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPDFMetadata.h"
 #include "SkPDFTypes.h"
 
@@ skipping 165 matching lines @@
     HEXIFY(data, ptr, gHex, 2);
     *ptr++ = '-';
     HEXIFY(data, ptr, gHex, 6);
     SkASSERT(ptr == buffer + 36);
     SkASSERT(data == uuid.fData + 16);
     return SkString(buffer, 36);
 }
 #undef HEXIFY
 
 namespace {
-class PDFXMLObject : public SkPDFObject {
+class PDFXMLObject final : public SkPDFObject {
 public:
     PDFXMLObject(SkString xml) : fXML(skstd::move(xml)) {}
     void emitObject(SkWStream* stream,
                     const SkPDFObjNumMap& omap,
                     const SkPDFSubstituteMap& smap) const override {
         SkPDFDict dict("Metadata");
         dict.insertName("Subtype", "XML");
         dict.insertInt("Length", fXML.size());
         dict.emitObject(stream, omap, smap);
         static const char streamBegin[] = " stream\n";
@@ skipping 144 matching lines @@
     SkString instanceID = uuid_to_string(instance);
     SkASSERT(0 == count_xml_escape_size(instanceID));
     return new PDFXMLObject(sk_string_printf(
             templateString, modificationDate.c_str(), creationDate.c_str(),
             metadataDate.c_str(), creator.c_str(), title.c_str(),
             subject.c_str(), author.c_str(), keywords1.c_str(),
             documentID.c_str(), instanceID.c_str(), keywords2.c_str()));
 }
 
 #endif  // SK_PDF_GENERATE_PDFA