Remove content::NotificationObserver dependency from most Prefs code.

base/files/important_file_writer.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_FILES_IMPORTANT_FILE_WRITER_H_
 #define BASE_FILES_IMPORTANT_FILE_WRITER_H_
 
 #include <string>
 
 #include "base/base_export.h"
@@ skipping 22 matching lines @@
 // To be safe, we don't start with writing directly to F. Instead, we write to
 // to a temporary file. Only after that write is successful, we rename the
 // temporary file to target filename.
 //
 // If you want to know more about this approach and ext3/ext4 fsync issues, see
 // http://valhenson.livejournal.com/37921.html
 class BASE_EXPORT ImportantFileWriter : public NonThreadSafe {
  public:
   // Used by ScheduleSave to lazily provide the data to be saved. Allows us
   // to also batch data serializations.
-  class DataSerializer {
+  class BASE_EXPORT DataSerializer {
    public:
     // Should put serialized string in |data| and return true on successful
     // serialization. Will be called on the same thread on which
     // ImportantFileWriter has been created.
     virtual bool SerializeData(std::string* data) = 0;
 
    protected:
     virtual ~DataSerializer() {}
   };
 
@@ skipping 53 matching lines @@
 
   // Time delta after which scheduled data will be written to disk.
   TimeDelta commit_interval_;
 
   DISALLOW_COPY_AND_ASSIGN(ImportantFileWriter);
 };
 
 }  // namespace base
 
 #endif  // BASE_FILES_IMPORTANT_FILE_WRITER_H_