Add TrackedPreferenceValidationDelegate

chrome/browser/prefs/tracked/tracked_atomic_preference.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PREFS_TRACKED_TRACKED_ATOMIC_PREFERENCE_H_
 #define CHROME_BROWSER_PREFS_TRACKED_TRACKED_ATOMIC_PREFERENCE_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 10 matching lines @@
       const std::string& pref_path,
       size_t reporting_id,
       size_t reporting_ids_count,
       PrefHashFilter::EnforcementLevel enforcement_level);
 
   // TrackedPreference implementation.
   virtual void OnNewValue(const base::Value* value,
                           PrefHashStoreTransaction* transaction) const OVERRIDE;
   virtual bool EnforceAndReport(
       base::DictionaryValue* pref_store_contents,
-      PrefHashStoreTransaction* transaction) const OVERRIDE;
+      PrefHashStoreTransaction* transaction,
+      TrackedPreferenceValidationObserver* observer) const OVERRIDE;

[erikwright (departed), 2014/05/14 00:39:26]

This could probably be a constructor parameter / member, right? It doesn't
change from call to call?

[grt (UTC plus 2), 2014/05/14 18:57:22]

I chose to make it a parameter here to avoid ownership issues. As a ctor
parameter, it either needs to be a naked pointer documented as being owned by
the TrackedPreference's owner, or it needs to be refcounted. Is there another
option I'm missing? Do you prefer one of those?

[erikwright (departed), 2014/05/14 21:24:06]

I prefer it being a raw pointer because there is no case for using a different
observer in different invocations. You can mention that it must outlive the
TrackedPreference if you like. But the TrackedPreference is owned by the
PrefHashFilter, so the lifecycle relationship is unambiguous.

[grt (UTC plus 2), 2014/05/15 01:43:11]

sgtm. Done.

 
  private:
   const std::string pref_path_;
   const TrackedPreferenceHelper helper_;
 
   DISALLOW_COPY_AND_ASSIGN(TrackedAtomicPreference);
 };
 
 #endif  // CHROME_BROWSER_PREFS_TRACKED_TRACKED_ATOMIC_PREFERENCE_H_