Let chrome_prefs handle Preferences initialization from master_preferences.

chrome/browser/prefs/pref_hash_filter.h

Index: chrome/browser/prefs/pref_hash_filter.h
diff --git a/chrome/browser/prefs/pref_hash_filter.h b/chrome/browser/prefs/pref_hash_filter.h
index 38caa89494c46290e20f30180868c4d00ead0e24..ebb9687ee03242b8ae780e6fa437b63d1fab10e3 100644
--- a/chrome/browser/prefs/pref_hash_filter.h
+++ b/chrome/browser/prefs/pref_hash_filter.h
@@ -74,9 +74,9 @@ class PrefHashFilter : public PrefFilter {
 
   virtual ~PrefHashFilter();
 
-  // Initializes the PrefHashStore with hashes of the tracked preferences
-  // in |pref_store|.
-  void Initialize(PrefStore* pref_store);
+  // Initializes the PrefHashStore with hashes of the tracked preferences in
+  // |pref_store|.
+  void Initialize(const PrefStore& pref_store);
 
   // PrefFilter implementation.
   virtual void FilterOnLoad(base::DictionaryValue* pref_store_contents)