Fix the PDF download button.

components/pdf/browser/pdf_web_contents_helper.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 COMPONENTS_PDF_BROWSER_PDF_WEB_CONTENTS_HELPER_H_
 #define COMPONENTS_PDF_BROWSER_PDF_WEB_CONTENTS_HELPER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 27 matching lines @@
 
   void ShowOpenInReaderPrompt(
       std::unique_ptr<OpenPDFInReaderPromptClient> prompt);
 
  private:
   PDFWebContentsHelper(content::WebContents* web_contents,
                        std::unique_ptr<PDFWebContentsHelperClient> client);
   ~PDFWebContentsHelper() override;
 
   // content::WebContentsObserver overrides:
-  bool OnMessageReceived(const IPC::Message& message) override;
+  bool OnMessageReceived(const IPC::Message& message,
+                         content::RenderFrameHost* render_frame_host) override;
   void DidNavigateMainFrame(
       const content::LoadCommittedDetails& details,
       const content::FrameNavigateParams& params) override;
 
   // Internal helpers ----------------------------------------------------------
 
   void UpdateLocationBar();
 
   // Message handlers.
   void OnHasUnsupportedFeature();
   void OnSaveURLAs(const GURL& url, const content::Referrer& referrer);
   void OnUpdateContentRestrictions(int content_restrictions);
 
   // The model for the confirmation prompt to open a PDF in Adobe Reader.
   std::unique_ptr<OpenPDFInReaderPromptClient> open_in_reader_prompt_;
   std::unique_ptr<PDFWebContentsHelperClient> client_;
 
   DISALLOW_COPY_AND_ASSIGN(PDFWebContentsHelper);
 };
 
 }  // namespace pdf
 
 #endif  // COMPONENTS_PDF_BROWSER_PDF_WEB_CONTENTS_HELPER_H_