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

chrome/browser/ui/views/location_bar/open_pdf_in_reader_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_LOCATION_BAR_OPEN_PDF_IN_READER_VIEW_H_
-#define CHROME_BROWSER_UI_VIEWS_LOCATION_BAR_OPEN_PDF_IN_READER_VIEW_H_
-
-#include "base/macros.h"
-#include "ui/views/controls/image_view.h"
-#include "ui/views/widget/widget_observer.h"
-
-class OpenPDFInReaderBubbleView;
-
-namespace content {
-class WebContents;
-}
-
-namespace pdf {
-class OpenPDFInReaderPromptClient;
-}
-
-// A Page Action image view for the "Open PDF in Reader" bubble.
-class OpenPDFInReaderView : public views::ImageView,
-                            public views::WidgetObserver {
- public:
-  OpenPDFInReaderView();
-  ~OpenPDFInReaderView() override;
-
-  void Update(content::WebContents* web_contents);
-
- private:
-  void ShowBubble();
-
-  // views::ImageView:
-  void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
-  bool OnMousePressed(const ui::MouseEvent& event) override;
-  void OnMouseReleased(const ui::MouseEvent& event) override;
-  bool OnKeyPressed(const ui::KeyEvent& event) override;
-  void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
-
-  // views::WidgetObserver:
-  void OnWidgetDestroying(views::Widget* widget) override;
-
-  OpenPDFInReaderBubbleView* bubble_;
-
-  // Weak pointer; owned by the PDFWebContentsHelper of the currently active
-  // tab.
-  pdf::OpenPDFInReaderPromptClient* model_;
-
-  DISALLOW_COPY_AND_ASSIGN(OpenPDFInReaderView);
-};
-
-#endif  // CHROME_BROWSER_UI_VIEWS_LOCATION_BAR_OPEN_PDF_IN_READER_VIEW_H_