Make a JsonPrefStore readable while mid-interception.

chrome/browser/prefs/tracked/tracked_preferences_migration.cc

Index: chrome/browser/prefs/tracked/tracked_preferences_migration.cc
diff --git a/chrome/browser/prefs/tracked/tracked_preferences_migration.cc b/chrome/browser/prefs/tracked/tracked_preferences_migration.cc
index c358256f06b4f50ff9e88b6045c82634d2b41586..079903d669dfb35df9d0c22c5cf6f07be11a2daa 100644
--- a/chrome/browser/prefs/tracked/tracked_preferences_migration.cc
+++ b/chrome/browser/prefs/tracked/tracked_preferences_migration.cc
@@ -47,7 +47,7 @@ class TrackedPreferencesMigrator
       PrefFilterID id,
       const InterceptablePrefFilter::FinalizeFilterOnLoadCallback&
           finalize_filter_on_load,
-      scoped_ptr<base::DictionaryValue> prefs);
+      base::DictionaryValue* prefs);
 
   // Proceeds with migration if both |unprotected_prefs_| and |protected_prefs_|
   // have been set.
@@ -68,8 +68,8 @@ class TrackedPreferencesMigrator
   InterceptablePrefFilter::FinalizeFilterOnLoadCallback
       finalize_protected_filter_on_load_;
 
-  scoped_ptr<base::DictionaryValue> unprotected_prefs_;
-  scoped_ptr<base::DictionaryValue> protected_prefs_;
+  base::DictionaryValue* unprotected_prefs_;
+  base::DictionaryValue* protected_prefs_;
 
   DISALLOW_COPY_AND_ASSIGN(TrackedPreferencesMigrator);
 };
@@ -157,7 +157,9 @@ TrackedPreferencesMigrator::TrackedPreferencesMigrator(
       register_on_successful_unprotected_store_write_callback_(
           register_on_successful_unprotected_store_write_callback),
       register_on_successful_protected_store_write_callback_(
-          register_on_successful_protected_store_write_callback) {
+          register_on_successful_protected_store_write_callback),
+      unprotected_prefs_(NULL),
+      protected_prefs_(NULL) {
   // The callbacks bound below will own this TrackedPreferencesMigrator by
   // reference.
   unprotected_pref_filter->InterceptNextFilterOnLoad(
@@ -176,15 +178,15 @@ void TrackedPreferencesMigrator::InterceptFilterOnLoad(
     PrefFilterID id,
     const InterceptablePrefFilter::FinalizeFilterOnLoadCallback&
         finalize_filter_on_load,
-    scoped_ptr<base::DictionaryValue> prefs) {
+    base::DictionaryValue* prefs) {
   switch (id) {
     case UNPROTECTED_PREF_FILTER:
       finalize_unprotected_filter_on_load_ = finalize_filter_on_load;
-      unprotected_prefs_ = prefs.Pass();
+      unprotected_prefs_ = prefs;
       break;
     case PROTECTED_PREF_FILTER:
       finalize_protected_filter_on_load_ = finalize_filter_on_load;
-      protected_prefs_ = prefs.Pass();
+      protected_prefs_ = prefs;
       break;
   }
 
@@ -199,23 +201,23 @@ void TrackedPreferencesMigrator::MigrateIfReady() {
   bool protected_prefs_need_cleanup = false;
   bool unprotected_prefs_altered = false;
   MigratePrefsFromOldToNewStore(unprotected_pref_names_,
-                                protected_prefs_.get(),
-                                unprotected_prefs_.get(),
+                                protected_prefs_,
+                                unprotected_prefs_,
                                 &protected_prefs_need_cleanup,
                                 &unprotected_prefs_altered);
   bool unprotected_prefs_need_cleanup = false;
   bool protected_prefs_altered = false;
   MigratePrefsFromOldToNewStore(protected_pref_names_,
-                                unprotected_prefs_.get(),
-                                protected_prefs_.get(),
+                                unprotected_prefs_,
+                                protected_prefs_,
                                 &unprotected_prefs_need_cleanup,
                                 &protected_prefs_altered);
 
-  // Hand the processed prefs back to their respective filters.
-  finalize_unprotected_filter_on_load_.Run(unprotected_prefs_.Pass(),
-                                           unprotected_prefs_altered);
-  finalize_protected_filter_on_load_.Run(protected_prefs_.Pass(),
-                                         protected_prefs_altered);
+  // Allow preference loading to proceed.
+  unprotected_prefs_ = NULL;
+  protected_prefs_ = NULL;
+  finalize_unprotected_filter_on_load_.Run(unprotected_prefs_altered);
+  finalize_protected_filter_on_load_.Run(protected_prefs_altered);
 
   if (unprotected_prefs_need_cleanup) {
     // Schedule a cleanup of the |protected_pref_names_| from the unprotected