Prepare ExternalPolicyDataUpdater and ResourceCache for blocking pool

chrome/browser/policy/cloud/external_policy_data_updater.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_POLICY_CLOUD_EXTERNAL_POLICY_DATA_UPDATER_H_
 #define CHROME_BROWSER_POLICY_CLOUD_EXTERNAL_POLICY_DATA_UPDATER_H_
 
 #include <map>
 #include <queue>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
-#include "base/threading/non_thread_safe.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
 namespace policy {
 
 class ExternalPolicyDataFetcher;
 
 // This class downloads external policy data. Given a |Request|, data is fetched
 // from the |url|, verified to not exceed |max_size| and to match the expected
 // |hash| and then handed to a callback that can do further verification before
 // finally deciding whether the fetched data is valid.
 // If a fetch is not successful or retrieves invalid data, retries are scheduled
 // with exponential backoff.
 // The actual fetching is handled by an ExternalPolicyDataFetcher, allowing this
 // class to run on a background thread where network I/O is not possible.
-class ExternalPolicyDataUpdater : public base::NonThreadSafe {
+class ExternalPolicyDataUpdater {
  public:
   struct Request {
    public:
     Request();
     Request(const std::string& url, const std::string& hash, int64 max_size);
 
     bool operator==(const Request& other) const;
 
     std::string url;
     std::string hash;
@@ skipping 72 matching lines @@
   // |True| once the destructor starts. Prevents jobs from being started during
   // shutdown.
   bool shutting_down_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalPolicyDataUpdater);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_CLOUD_EXTERNAL_POLICY_DATA_UPDATER_H_