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

components/prefs/pref_value_store.h

Index: components/prefs/pref_value_store.h
diff --git a/components/prefs/pref_value_store.h b/components/prefs/pref_value_store.h
index 39b6bf1870ee3fc06e1eb9f53a243284c6109334..3a2bf1594fa3c11025291f6cc7702e2f6ae9d103 100644
--- a/components/prefs/pref_value_store.h
+++ b/components/prefs/pref_value_store.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_VALUE_STORE_H_
-#define COMPONENTS_PREFS_PREF_VALUE_STORE_H_
+#ifndef BASE_PREFS_PREF_VALUE_STORE_H_
+#define BASE_PREFS_PREF_VALUE_STORE_H_
 
 #include <map>
 #include <string>
@@ -26,7 +26,7 @@
 //
 // Unless otherwise explicitly noted, all of the methods of this class must
 // be called on the UI thread.
-class COMPONENTS_PREFS_EXPORT PrefValueStore {
+class BASE_PREFS_EXPORT PrefValueStore {
  public:
   typedef base::Callback<void(const std::string&)> PrefChangedCallback;
 
@@ -257,4 +257,4 @@
   DISALLOW_COPY_AND_ASSIGN(PrefValueStore);
 };
 
-#endif  // COMPONENTS_PREFS_PREF_VALUE_STORE_H_
+#endif  // BASE_PREFS_PREF_VALUE_STORE_H_