PDF: Fix a crash from r372196 with the print preview PDFEngine client.

pdf/preview_mode_client.cc

 // Copyright (c) 2011 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/preview_mode_client.h"
 
 #include <stdint.h>
 
 #include "base/logging.h"
 
@@ skipping 120 matching lines @@
 
 void PreviewModeClient::DocumentLoadComplete(int page_count) {
   client_->PreviewDocumentLoadComplete();
 }
 
 void PreviewModeClient::DocumentLoadFailed() {
   client_->PreviewDocumentLoadFailed();
 }
 
 pp::Instance* PreviewModeClient::GetPluginInstance() {
-  NOTREACHED();
-  return NULL;
+  return nullptr;
 }
 
 void PreviewModeClient::DocumentHasUnsupportedFeature(
     const std::string& feature) {
   NOTREACHED();
 }
 
 void PreviewModeClient::DocumentLoadProgress(uint32_t available,
                                              uint32_t doc_size) {}
 
 void PreviewModeClient::FormTextFieldFocusChange(bool in_focus) {
   NOTREACHED();
 }
 
 bool PreviewModeClient::IsPrintPreview() {
   NOTREACHED();
   return false;
 }
 
 uint32_t PreviewModeClient::GetBackgroundColor() {
   NOTREACHED();
   return 0;
 }
 
 }  // namespace chrome_pdf