Make a JsonPrefStore readable while mid-interception.

base/prefs/pref_filter.h

Index: base/prefs/pref_filter.h
diff --git a/base/prefs/pref_filter.h b/base/prefs/pref_filter.h
index 1020029131ab3daaec1f3abbfa322781915d9abf..d3fc8f1b7681b1c167c22f65e5bab11cf9f8c283 100644
--- a/base/prefs/pref_filter.h
+++ b/base/prefs/pref_filter.h
@@ -20,25 +20,26 @@ class Value;
 // Currently supported only by JsonPrefStore.
 class BASE_PREFS_EXPORT PrefFilter {
  public:
-  // A callback to be invoked when |prefs| have been read (and possibly
+  // A callback to be invoked when prefs have been read (and possibly
   // pre-modified) and are now ready to be handed back to this callback's
   // builder. |schedule_write| indicates whether a write should be immediately
-  // scheduled (typically because the |prefs| were pre-modified).
-  typedef base::Callback<void(scoped_ptr<base::DictionaryValue> prefs,
-                              bool schedule_write)> PostFilterOnLoadCallback;
+  // scheduled (typically because the prefs were pre-modified).
+  typedef base::Callback<void(bool schedule_write)> PostFilterOnLoadCallback;
 
   virtual ~PrefFilter() {}
 
-  // This method is given ownership of the |pref_store_contents| read from disk
-  // before the underlying PersistentPrefStore gets to use them. It must hand
-  // them back via |post_filter_on_load_callback|, but may modify them first.
+  // This method is given a reference to the |pref_store_contents| read from
+  // disk

[gab, 2014/06/11 21:12:55]

nit: fix early line break

+  // before other observers and clients of the PersistentPrefStore use them. It
+  // must eventually call |post_filter_on_load_callback|, but may modify the
+  // prefs first.
   // Note: This method is asynchronous, which may make calls like
   // PersistentPrefStore::ReadPrefs() asynchronous. The owner of filtered
   // PersistentPrefStores should handle this to make the reads look synchronous
   // to external users (see SegregatedPrefStore::ReadPrefs() for an example).
   virtual void FilterOnLoad(
       const PostFilterOnLoadCallback& post_filter_on_load_callback,
-      scoped_ptr<base::DictionaryValue> pref_store_contents) = 0;
+      base::DictionaryValue* pref_store_contents) = 0;
 
   // Receives notification when a pref store value is changed, before Observers
   // are notified.