Fix two URLRequestJob subclasses that didn't support cancellation

components/about_handler/url_request_about_job.cc

 // 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.
 
 // Simple implementation of about: protocol handler that treats everything as
 // about:blank.  No other about: features should be available to web content,
 // so they're not implemented here.
 
 #include "components/about_handler/url_request_about_job.h"
 
@@ skipping 12 matching lines @@
 }
 
 void URLRequestAboutJob::Start() {
   // Start reading asynchronously so that all error reporting and data
   // callbacks happen as they would for network requests.
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(&URLRequestAboutJob::StartAsync, weak_factory_.GetWeakPtr()));
 }
 
+void URLRequestAboutJob::Kill() {
+  weak_factory_.InvalidateWeakPtrs();
+  URLRequestJob::Kill();
+}
+
 bool URLRequestAboutJob::GetMimeType(std::string* mime_type) const {
   *mime_type = "text/html";
   return true;
 }
 
 URLRequestAboutJob::~URLRequestAboutJob() {
 }
 
 void URLRequestAboutJob::StartAsync() {
   NotifyHeadersComplete();
 }
 
 }  // namespace about_handler