Introduce PrefRegistrySyncable, simplifying PrefServiceSyncable.

chrome/browser/prefs/proxy_policy_unittest.cc

Index: chrome/browser/prefs/proxy_policy_unittest.cc
diff --git a/chrome/browser/prefs/proxy_policy_unittest.cc b/chrome/browser/prefs/proxy_policy_unittest.cc
index 165274210d2ba12b2d1f4fc3517c1c0d08b922cc..88c92d350fc375e7c467cebc903389afa42a1305 100644
--- a/chrome/browser/prefs/proxy_policy_unittest.cc
+++ b/chrome/browser/prefs/proxy_policy_unittest.cc
@@ -3,12 +3,14 @@
 // found in the LICENSE file.
 
 #include "base/command_line.h"
+#include "base/memory/ref_counted.h"
 #include "chrome/browser/policy/mock_configuration_policy_provider.h"
 #include "chrome/browser/policy/policy_map.h"
 #include "chrome/browser/policy/policy_service_impl.h"
 #include "chrome/browser/prefs/browser_prefs.h"
-#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/prefs/pref_registry_syncable.h"
 #include "chrome/browser/prefs/pref_service_mock_builder.h"
+#include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/prefs/proxy_config_dictionary.h"
 #include "chrome/browser/prefs/proxy_prefs.h"
 #include "chrome/common/chrome_switches.h"
@@ -97,8 +99,9 @@ class ProxyPolicyTest : public testing::Test {
     builder.WithCommandLine(&command_line_);
     if (with_managed_policies)
       builder.WithManagedPolicies(policy_service_.get());
-    PrefServiceSyncable* prefs = builder.CreateSyncable();
-    chrome::RegisterUserPrefs(prefs);
+    scoped_refptr<PrefRegistrySyncable> registry(new PrefRegistrySyncable);
+    PrefServiceSyncable* prefs = builder.CreateSyncable(registry);
+    chrome::RegisterUserPrefs(prefs, registry);
     return prefs;
   }