Revert of Force HostContentSettingsMap to be destroyed on its owning thread.

components/keyed_service/core/refcounted_keyed_service.cc

 // Copyright 2014 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/keyed_service/core/refcounted_keyed_service.h"
 
-#include <utility>
+#include "base/location.h"
+#include "base/threading/thread_task_runner_handle.h"
 
 namespace impl {
 
 // static
 void RefcountedKeyedServiceTraits::Destruct(const RefcountedKeyedService* obj) {
-  if (obj->task_runner_ && !obj->task_runner_->RunsTasksOnCurrentThread()) {
+  if (obj->task_runner_.get() != nullptr &&
+      obj->task_runner_.get() != base::ThreadTaskRunnerHandle::Get()) {
     obj->task_runner_->DeleteSoon(FROM_HERE, obj);
   } else {
     delete obj;
   }
 }
 
 }  // namespace impl
 
 RefcountedKeyedService::RefcountedKeyedService() : task_runner_(nullptr) {
 }
 
 RefcountedKeyedService::RefcountedKeyedService(
-    scoped_refptr<base::SequencedTaskRunner> task_runner)
-    : task_runner_(std::move(task_runner)) {}
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner)
+    : task_runner_(task_runner) {
+}
 
-RefcountedKeyedService::~RefcountedKeyedService() = default;
+RefcountedKeyedService::~RefcountedKeyedService() {
+}