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

chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm

 // Copyright 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.
 
 #import "chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.h"
 
 #include "base/bind.h"
 #import "base/mac/mac_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
@@ skipping 238 matching lines @@
 
 bool LocationBarViewMac::ShowPageActionPopup(
     const extensions::Extension* extension, bool grant_active_tab) {
   for (const auto& decoration : page_action_decorations_) {
     if (decoration->GetExtension() == extension)
       return decoration->ActivatePageAction(grant_active_tab);
   }
   return false;
 }
 
-void LocationBarViewMac::UpdateOpenPDFInReaderPrompt() {
-  // Not implemented on Mac.
-}
-
 void LocationBarViewMac::SaveStateToContents(WebContents* contents) {
   // TODO(shess): Why SaveStateToContents vs SaveStateToTab?
   omnibox_view_->SaveStateToTab(contents);
 }
 
 void LocationBarViewMac::Revert() {
   omnibox_view_->RevertAll();
 }
 
 const OmniboxView* LocationBarViewMac::GetOmniboxView() const {
@@ skipping 676 matching lines @@
     OnDecorationsChanged();
 }
 
 std::vector<NSView*> LocationBarViewMac::GetDecorationAccessibilityViews() {
   std::vector<LocationBarDecoration*> decorations = GetDecorations();
   std::vector<NSView*> views;
   for (auto* decoration : decorations)
     views.push_back(decoration->GetAccessibilityView());
   return views;
 }