Fix crash on app list start page contents not existing.

chrome/browser/ui/app_list/start_page_service.cc

 // Copyright 2013 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 "chrome/browser/ui/app_list/start_page_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 637 matching lines @@
     base::DictionaryValue* doodle_dictionary = nullptr;
     // Use the supplied TTL as the recheck delay if available.
     if (doodle_json->GetAsDictionary(&doodle_dictionary)) {
       int time_to_live = 0;
       if (doodle_dictionary->GetInteger("ddljson.time_to_live_ms",
                                         &time_to_live)) {
         recheck_delay = base::TimeDelta::FromMilliseconds(time_to_live);
       }
     }
 
-    contents_->GetWebUI()->CallJavascriptFunction(
-        "appList.startPage.onAppListDoodleUpdated", *doodle_json,
-        base::StringValue(
-            UIThreadSearchTermsData(profile_).GoogleBaseURLValue()));
+    if (contents_ && contents_->GetWebUI()) {
+      contents_->GetWebUI()->CallJavascriptFunction(
+          "appList.startPage.onAppListDoodleUpdated", *doodle_json,
+          base::StringValue(
+              UIThreadSearchTermsData(profile_).GoogleBaseURLValue()));
+    }
   }
 
   // Check for a new doodle.
   content::BrowserThread::PostDelayedTask(
       content::BrowserThread::UI, FROM_HERE,
       base::Bind(&StartPageService::FetchDoodleJson,
                  weak_factory_.GetWeakPtr()),
       recheck_delay);
 }
 
 }  // namespace app_list