Split PrefService into PrefService, PrefServiceSimple and PrefServiceSyncable.

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index fb7921a71cb25cf2111cf19e6d0a737bcca4a5e6..25763a37a75d9fc20e719e66fe46b3f476f7fbbd 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -23,7 +23,7 @@
 class ChromeNetLog;
 class CommandLine;
 class PrefProxyConfigTrackerImpl;
-class PrefService;
+class PrefServiceSimple;
 class SystemURLRequestContextGetter;
 
 namespace chrome_browser_net {
@@ -165,7 +165,7 @@ class IOThread : public content::BrowserThreadDelegate {
   };
 
   // |net_log| must either outlive the IOThread or be NULL.
-  IOThread(PrefService* local_state,
+  IOThread(PrefServiceSimple* local_state,
            policy::PolicyService* policy_service,
            ChromeNetLog* net_log,
            extensions::EventRouterForwarder* extension_event_router_forwarder);
@@ -230,7 +230,7 @@ class IOThread : public content::BrowserThreadDelegate {
   // SystemRequestContext state has been initialized on the UI thread.
   void InitSystemRequestContextOnIOThread();
 
-  static void RegisterPrefs(PrefService* local_state);
+  static void RegisterPrefs(PrefServiceSimple* local_state);
 
   net::HttpAuthHandlerFactory* CreateDefaultAuthHandlerFactory(
       net::HostResolver* resolver);