Fix HostZoomMap related crash from r86367. Re-enable PDFBrowserTest.Slow_Loading.

content/browser/host_zoom_map.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 <cmath>
 
 #include "content/browser/host_zoom_map.h"
 
 #include "base/string_piece.h"
 #include "base/utf_string_conversions.h"
@@ skipping 72 matching lines @@
 
     if (level && i == temporary_zoom_levels_.size()) {
       TemporaryZoomLevel temp;
       temp.render_process_id = render_process_id;
       temp.render_view_id = render_view_id;
       temp.zoom_level = level;
       temporary_zoom_levels_.push_back(temp);
     }
   }
 
+  std::string host;
   NotificationService::current()->Notify(NotificationType::ZOOM_LEVEL_CHANGED,
                                          Source<HostZoomMap>(this),
-                                         NotificationService::NoDetails());
+                                         Details<const std::string>(&host));
+
 }
 
 void HostZoomMap::Observe(
     NotificationType type,
     const NotificationSource& source,
     const NotificationDetails& details) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   switch (type.value) {
     case NotificationType::RENDER_VIEW_HOST_WILL_CLOSE_RENDER_VIEW: {
@@ skipping 10 matching lines @@
       }
       break;
     }
     default:
       NOTREACHED() << "Unexpected preference observed.";
   }
 }
 
 HostZoomMap::~HostZoomMap() {
 }