Revert of Pref service: add support for tracked prefs.

chrome/browser/profiles/profile_impl.h

Index: chrome/browser/profiles/profile_impl.h
diff --git a/chrome/browser/profiles/profile_impl.h b/chrome/browser/profiles/profile_impl.h
index 7956e02e5246a6b9660071a8cb14e548e0ced412..54093b9ce0309d2847af68e2365c746b9afa8582 100644
--- a/chrome/browser/profiles/profile_impl.h
+++ b/chrome/browser/profiles/profile_impl.h
@@ -48,6 +48,12 @@
 class ConfigurationPolicyProvider;
 class ProfilePolicyConnector;
 class SchemaRegistryService;
+}
+
+namespace prefs {
+namespace mojom {
+class TrackedPreferenceValidationDelegate;
+}
 }
 
 namespace ssl_config {
@@ -216,6 +222,11 @@
       configuration_policy_provider_;
   std::unique_ptr<policy::ProfilePolicyConnector> profile_policy_connector_;
 
+  // Keep |pref_validation_delegate_| above |prefs_| so that the former outlives
+  // the latter.
+  std::unique_ptr<prefs::mojom::TrackedPreferenceValidationDelegate>
+      pref_validation_delegate_;
+
   // Keep |prefs_| on top for destruction order because |extension_prefs_|,
   // |io_data_| and others store pointers to |prefs_| and shall be destructed
   // first.