Fix ntp-tiles-internals crash in incognito mode

components/ntp_tiles/webui/ntp_tiles_internals_message_handler.cc

 // Copyright 2016 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 "components/ntp_tiles/webui/ntp_tiles_internals_message_handler.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 26 matching lines @@
       base::Bind(&NTPTilesInternalsMessageHandler::HandleRegisterForEvents,
                  base::Unretained(this)));
 
   client_->RegisterMessageCallback(
       "update", base::Bind(&NTPTilesInternalsMessageHandler::HandleUpdate,
                            base::Unretained(this)));
 }
 
 void NTPTilesInternalsMessageHandler::HandleRegisterForEvents(
     const base::ListValue* args) {
+  if (!client_->SupportsNTPTiles()) {
+    return;
+  }
   DCHECK(args->empty());
 
   SendSourceInfo();
 
   most_visited_sites_ = client_->MakeMostVisitedSites();
   most_visited_sites_->SetMostVisitedURLsObserver(this, site_count_);
 }
 
 void NTPTilesInternalsMessageHandler::HandleUpdate(
     const base::ListValue* args) {
+  if (!client_->SupportsNTPTiles()) {
+    return;
+  }
   const base::DictionaryValue* dict = nullptr;
   DCHECK_EQ(1u, args->GetSize());
   args->GetDictionary(0, &dict);
   DCHECK(dict);
 
   PrefService* prefs = client_->GetPrefs();
 
   if (client_->DoesSourceExist(ntp_tiles::NTPTileSource::POPULAR)) {
     std::string url;
     dict->GetString("popular.overrideURL", &url);
@@ skipping 84 matching lines @@
 
 void NTPTilesInternalsMessageHandler::OnMostVisitedURLsAvailable(
     const NTPTilesVector& tiles) {
   SendTiles(tiles);
 }
 
 void NTPTilesInternalsMessageHandler::OnIconMadeAvailable(
     const GURL& site_url) {}
 
 }  // namespace ntp_tiles