Revert of Delete base/prefs and update callers to use components.

components/prefs/pref_change_registrar.h

Index: components/prefs/pref_change_registrar.h
diff --git a/components/prefs/pref_change_registrar.h b/components/prefs/pref_change_registrar.h
index 2ae3b195e3023bcfb93c9ea9890e370ba72f0421..5e5b6a8c983e09d521e828ee7b06bd5b4cb93eff 100644
--- a/components/prefs/pref_change_registrar.h
+++ b/components/prefs/pref_change_registrar.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
-#define COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
+#ifndef BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
+#define BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
 
 #include <map>
 #include <string>
@@ -19,7 +19,7 @@
 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
 // manages observers of preference changes. When the Registrar is destroyed,
 // all registered observers are automatically unregistered with the PrefStore.
-class COMPONENTS_PREFS_EXPORT PrefChangeRegistrar : public PrefObserver {
+class BASE_PREFS_EXPORT PrefChangeRegistrar : public PrefObserver {
  public:
   // You can register this type of callback if you need to know the
   // path of the preference that is changing.
@@ -78,4 +78,4 @@
   DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
 };
 
-#endif  // COMPONENTS_PREFS_PREF_CHANGE_REGISTRAR_H_
+#endif  // BASE_PREFS_PREF_CHANGE_REGISTRAR_H_