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 78d85fe0c34d5fb6926cc857f961d25bf110bc38..7cdf2cf85032326673962582c89036c8d86e8f56 100644
--- a/chrome/browser/profiles/off_the_record_profile_impl.h
+++ b/chrome/browser/profiles/off_the_record_profile_impl.h
@@ -16,6 +16,8 @@
 using base::Time;
 using base::TimeDelta;
 
+class PrefServiceSyncable;
+
 ////////////////////////////////////////////////////////////////////////////////
 //
 // OffTheRecordProfileImpl is a profile subclass that wraps an existing profile
@@ -43,8 +45,8 @@ 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* CreateRequestContext(