Move ImportantFileWriter to base/. It now has two consumers, base/prefs and chrome/.

base/prefs/json_pref_store.h

 // 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.
 
 #ifndef BASE_PREFS_JSON_PREF_STORE_H_
 #define BASE_PREFS_JSON_PREF_STORE_H_
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
+#include "base/files/important_file_writer.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/message_loop_proxy.h"
 #include "base/observer_list.h"
 #include "base/prefs/persistent_pref_store.h"
-#include "chrome/common/important_file_writer.h"
 
 namespace base {
 class DictionaryValue;
 class MessageLoopProxy;
 class Value;
 }
 
 class FilePath;
 
 // A writable PrefStore implementation that is used for user preferences.
 class JsonPrefStore : public PersistentPrefStore,
-                      public ImportantFileWriter::DataSerializer {
+                      public base::ImportantFileWriter::DataSerializer {
  public:
   // |file_message_loop_proxy| is the MessageLoopProxy for a thread on which
   // file I/O can be done.
   JsonPrefStore(const FilePath& pref_filename,
                 base::MessageLoopProxy* file_message_loop_proxy);
 
   // PrefStore overrides:
   virtual ReadResult GetValue(const std::string& key,
                               const base::Value** result) const OVERRIDE;
   virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
@@ skipping 29 matching lines @@
   virtual bool SerializeData(std::string* output) OVERRIDE;
 
   FilePath path_;
   scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy_;
 
   scoped_ptr<base::DictionaryValue> prefs_;
 
   bool read_only_;
 
   // Helper for safely writing pref data.
-  ImportantFileWriter writer_;
+  base::ImportantFileWriter writer_;
 
   ObserverList<PrefStore::Observer, true> observers_;
 
   scoped_ptr<ReadErrorDelegate> error_delegate_;
 
   bool initialized_;
   PrefReadError read_error_;
 
   std::set<std::string> keys_need_empty_value_;
 
   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 };
 
 #endif  // BASE_PREFS_JSON_PREF_STORE_H_