Introduce PrefRegistrySyncable, simplifying PrefServiceSyncable.

chrome/browser/profiles/off_the_record_profile_impl.h

Index: chrome/browser/profiles/off_the_record_profile_impl.h
diff --git a/chrome/browser/profiles/off_the_record_profile_impl.h b/chrome/browser/profiles/off_the_record_profile_impl.h
index 3066eaeffeae95a8b41ae6806875965b889c0f49..09459782333b965a40730f11f0e0229964d5c274 100644
--- a/chrome/browser/profiles/off_the_record_profile_impl.h
+++ b/chrome/browser/profiles/off_the_record_profile_impl.h
@@ -17,6 +17,8 @@
 using base::Time;
 using base::TimeDelta;
 
+class PrefServiceSyncable;
+
 ////////////////////////////////////////////////////////////////////////////////
 //
 // OffTheRecordProfileImpl is a profile subclass that wraps an existing profile
@@ -45,8 +47,8 @@ class OffTheRecordProfileImpl : public Profile,
   virtual policy::ManagedModePolicyProvider*
       GetManagedModePolicyProvider() OVERRIDE;
   virtual policy::PolicyService* GetPolicyService() OVERRIDE;
-  virtual PrefServiceSyncable* GetPrefs() OVERRIDE;
-  virtual PrefServiceSyncable* GetOffTheRecordPrefs() OVERRIDE;
+  virtual PrefService* GetPrefs() OVERRIDE;
+  virtual PrefService* GetOffTheRecordPrefs() OVERRIDE;
   virtual net::URLRequestContextGetter*
       GetRequestContextForExtensions() OVERRIDE;
   virtual net::URLRequestContextGetter* GetRequestContextForStoragePartition(