Remove dead code since PDFWebContentsHelper::ShowOpenInReaderPrompt isn't called anymore.

chrome/browser/ui/views/open_pdf_in_reader_bubble_view.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 CHROME_BROWSER_UI_VIEWS_OPEN_PDF_IN_READER_BUBBLE_VIEW_H_
-#define CHROME_BROWSER_UI_VIEWS_OPEN_PDF_IN_READER_BUBBLE_VIEW_H_
-
-#include "base/macros.h"
-#include "ui/views/bubble/bubble_dialog_delegate.h"
-#include "ui/views/controls/link_listener.h"
-
-namespace pdf {
-class OpenPDFInReaderPromptClient;
-}
-
-class OpenPDFInReaderBubbleView : public views::BubbleDialogDelegateView,
-                                  public views::LinkListener {
- public:
-  OpenPDFInReaderBubbleView(views::View* anchor_view,
-                            pdf::OpenPDFInReaderPromptClient* model);
-  ~OpenPDFInReaderBubbleView() override;
-
- protected:
-  // views::BubbleDialogDelegateView:
-  void Init() override;
-  bool Cancel() override;
-  int GetDialogButtons() const override;
-  base::string16 GetDialogButtonLabel(ui::DialogButton button) const override;
-
-  // views::LinkListener:
-  void LinkClicked(views::Link* source, int event_flags) override;
-
- private:
-  // Weak pointer; owned by the PDFWebContentsHelper of the currently active
-  // tab.
-  pdf::OpenPDFInReaderPromptClient* model_;
-
-  views::Link* open_in_reader_link_;
-
-  DISALLOW_COPY_AND_ASSIGN(OpenPDFInReaderBubbleView);
-};
-
-#endif  // CHROME_BROWSER_UI_VIEWS_OPEN_PDF_IN_READER_BUBBLE_VIEW_H_