No longer register app window placement preference keys on the fly.

base/prefs/pref_service.h

Index: base/prefs/pref_service.h
diff --git a/base/prefs/pref_service.h b/base/prefs/pref_service.h
index 186433c1b62907c16eb3360ca8d567ca2b1a07a6..f5a727a167a5f91bdefa9e2fcaf079bec5d9f2a7 100644
--- a/base/prefs/pref_service.h
+++ b/base/prefs/pref_service.h
@@ -270,6 +270,11 @@ class BASE_PREFS_EXPORT PrefService : public base::NonThreadSafe {
   // implemented in chrome/browser/prefs/browser_prefs.cc.
   PrefRegistry* DeprecatedGetPrefRegistry();
 
+  // This is only to be used to migrate unregistered prefs to become registered.

[Bernhard Bauer, 2014/09/04 11:06:02]

One thing we could do to ensure no one else uses this method would be to make it
private and friend the caller. WDYT?

[dgrogan, 2014/09/04 20:26:33]

Changed (for this patchset, at least). I don't like two things about it. (1)
When we remove the method it will be easy to forget about the "friend" line. (2)
The declarations are ugly and indicate a layering violation, though none exists.
I'm going to look into using PrefFilter to obviate this issue.

+  // TODO(dgrogan): Remove after a suitable migration period. See

[Bernhard Bauer, 2014/09/04 11:06:02]

Can you add what a suitable migration period is? (E.g. which milestone) That
way, even if we both forget about this, someone else who comes across this code
in ten years can fix it.

[dgrogan, 2014/09/04 20:26:32]

Done.

+  // http://crbug.com/167256.
+  scoped_ptr<base::DictionaryValue> GetBrowserDictionary() const;

[dgrogan, 2014/09/04 00:50:51]

This is the ugliest. See browser_ui_prefs.cc for its usage.

+
  protected:
   // The PrefNotifier handles registering and notifying preference observers.
   // It is created and owned by this PrefService. Subclasses may access it for