Revert of Move base/prefs to components/prefs

base/prefs/pref_observer.h

Index: base/prefs/pref_observer.h
diff --git a/base/prefs/pref_observer.h b/base/prefs/pref_observer.h
index df5d1af1ed824d5f2afc34789b112ae73ab35a7c..5d8f5b63dc3c9cb363a546ee10ddb92787765937 100644
--- a/base/prefs/pref_observer.h
+++ b/base/prefs/pref_observer.h
@@ -2,6 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// TODO(brettw) remove this forwarding header when prefs is completely moved to
-// components.
-#include "components/prefs/pref_observer.h"
+#ifndef BASE_PREFS_PREF_OBSERVER_H_
+#define BASE_PREFS_PREF_OBSERVER_H_
+
+#include <string>
+
+class PrefService;
+
+// Used internally to the Prefs subsystem to pass preference change
+// notifications between PrefService, PrefNotifierImpl and
+// PrefChangeRegistrar.
+class PrefObserver {
+ public:
+  virtual void OnPreferenceChanged(PrefService* service,
+                                   const std::string& pref_name) = 0;
+};
+
+#endif  // BASE_PREFS_PREF_OBSERVER_H_