Introduce a new framework for back-and-forth tracked/protected preferences migration.

chrome/browser/prefs/tracked/segregated_pref_store.cc

 // 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.
 
 #include "chrome/browser/prefs/tracked/segregated_pref_store.h"
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/values.h"
 
@@ skipping 17 matching lines @@
 void SegregatedPrefStore::AggregatingObserver::OnInitializationCompleted(
     bool succeeded) {
   if (succeeded)
     ++successful_sub_initializations_;
   else
     ++failed_sub_initializations_;
 
   DCHECK_LE(failed_sub_initializations_ + successful_sub_initializations_, 2);
 
   if (failed_sub_initializations_ + successful_sub_initializations_ == 2) {
-    if (!outer_->on_initialization_.is_null())
-      outer_->on_initialization_.Run();
-
     if (successful_sub_initializations_ == 2 && outer_->read_error_delegate_) {
       PersistentPrefStore::PrefReadError read_error = outer_->GetReadError();
       if (read_error != PersistentPrefStore::PREF_READ_ERROR_NONE)
         outer_->read_error_delegate_->OnError(read_error);
     }
 
     FOR_EACH_OBSERVER(
         PrefStore::Observer,
         outer_->observers_,
         OnInitializationCompleted(successful_sub_initializations_ == 2));
   }
 }
 
 SegregatedPrefStore::SegregatedPrefStore(
     const scoped_refptr<PersistentPrefStore>& default_pref_store,
     const scoped_refptr<PersistentPrefStore>& selected_pref_store,
-    const std::set<std::string>& selected_pref_names,
-    const base::Closure& on_initialization)
+    const std::set<std::string>& selected_pref_names)
     : default_pref_store_(default_pref_store),
       selected_pref_store_(selected_pref_store),
       selected_preference_names_(selected_pref_names),
-      on_initialization_(on_initialization),
       aggregating_observer_(this) {
-
   default_pref_store_->AddObserver(&aggregating_observer_);
   selected_pref_store_->AddObserver(&aggregating_observer_);
 }
 
 void SegregatedPrefStore::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
 void SegregatedPrefStore::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
@@ skipping 46 matching lines @@
   if (read_error == PersistentPrefStore::PREF_READ_ERROR_NONE) {
     read_error = selected_pref_store_->GetReadError();
     // Ignore NO_FILE from selected_pref_store_.
     if (read_error == PersistentPrefStore::PREF_READ_ERROR_NO_FILE)
       read_error = PersistentPrefStore::PREF_READ_ERROR_NONE;
   }
   return read_error;
 }
 
 PersistentPrefStore::PrefReadError SegregatedPrefStore::ReadPrefs() {
+  // Note: Both of these stores own PrefFilters which makes ReadPrefs
+  // asynchronous. This is okay in this case as only the first call will be
+  // truly asynchronous, the second call will then unblock the migration in
+  // TrackedPreferencesMigrator and complete synchronously.
   default_pref_store_->ReadPrefs();
-  selected_pref_store_->ReadPrefs();
+  PersistentPrefStore::PrefReadError selected_store_read_error =
+      selected_pref_store_->ReadPrefs();
+  DCHECK_NE(PersistentPrefStore::PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE,
+            selected_store_read_error);
 
   return GetReadError();
 }
 
 void SegregatedPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
   read_error_delegate_.reset(error_delegate);
   default_pref_store_->ReadPrefsAsync(NULL);
   selected_pref_store_->ReadPrefsAsync(NULL);
 }
 
 void SegregatedPrefStore::CommitPendingWrite() {
   default_pref_store_->CommitPendingWrite();
   selected_pref_store_->CommitPendingWrite();
 }
 
 SegregatedPrefStore::~SegregatedPrefStore() {
   default_pref_store_->RemoveObserver(&aggregating_observer_);
   selected_pref_store_->RemoveObserver(&aggregating_observer_);
 }
 
+PersistentPrefStore* SegregatedPrefStore::StoreForKey(const std::string& key) {
+  return ContainsKey(selected_preference_names_, key) ? selected_pref_store_
+                                                      : default_pref_store_;
+}
+
 const PersistentPrefStore* SegregatedPrefStore::StoreForKey(
     const std::string& key) const {
-  if (ContainsKey(selected_preference_names_, key) ||
-      selected_pref_store_->GetValue(key, NULL)) {
-    return selected_pref_store_.get();
-  }
-  return default_pref_store_.get();
+  return ContainsKey(selected_preference_names_, key) ? selected_pref_store_
+                                                      : default_pref_store_;
 }
-
-PersistentPrefStore* SegregatedPrefStore::StoreForKey(const std::string& key) {
-  if (ContainsKey(selected_preference_names_, key))
-    return selected_pref_store_.get();
-
-  // Check if this unselected value was previously selected. If so, migrate it
-  // back to the unselected store.
-  // It's hard to do this in a single pass at startup because PrefStore does not
-  // permit us to enumerate its contents.
-  const base::Value* value = NULL;
-  if (selected_pref_store_->GetValue(key, &value)) {
-    default_pref_store_->SetValue(key, value->DeepCopy());
-    // Commit |default_pref_store_| to guarantee that the migrated value is
-    // flushed to disk before the removal from |selected_pref_store_| is
-    // eventually flushed to disk.
-    default_pref_store_->CommitPendingWrite();
-
-    value = NULL;
-    selected_pref_store_->RemoveValue(key);
-  }
-
-  return default_pref_store_.get();
-}