Add histograms to track synced pref changes.

chrome/browser/prefs/synced_pref_change_registrar.cc

Index: chrome/browser/prefs/synced_pref_change_registrar.cc
diff --git a/chrome/browser/prefs/synced_pref_change_registrar.cc b/chrome/browser/prefs/synced_pref_change_registrar.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6245a5f754e739e68b3bd349e69d91fea5a8f4c3
--- /dev/null
+++ b/chrome/browser/prefs/synced_pref_change_registrar.cc
@@ -0,0 +1,63 @@
+// Copyright (c) 2013 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/synced_pref_change_registrar.h"
+
+#include "base/bind.h"
+
+namespace {
+
+void InvokeUnnamedCallback(
+    const SyncedPrefChangeRegistrar::ChangeCallback& callback,
+    const std::string& path, bool from_sync) {
+  callback.Run(from_sync);
+}
+
+}  // namespace
+
+SyncedPrefChangeRegistrar::SyncedPrefChangeRegistrar(
+    PrefServiceSyncable* pref_service) {
+  pref_service_ = pref_service;
+}
+
+SyncedPrefChangeRegistrar::~SyncedPrefChangeRegistrar() {
+  RemoveAll();
+}
+
+void SyncedPrefChangeRegistrar::Add(const char *path,
+    const ChangeCallback& callback) {
+  Add(path, base::Bind(InvokeUnnamedCallback, callback));
+}
+
+void SyncedPrefChangeRegistrar::Add(const char *path,
+    const NamedChangeCallback& callback) {
+  DCHECK(!IsObserved(path));
+  observers_[path] = callback;
+  pref_service_->AddSyncedPrefObserver(path, this);
+}
+
+void SyncedPrefChangeRegistrar::Remove(const char *path) {
+  observers_.erase(path);
+  pref_service_->RemoveSyncedPrefObserver(path, this);
+}
+
+void SyncedPrefChangeRegistrar::RemoveAll() {
+  for (ObserverMap::iterator iter = observers_.begin();
+      iter != observers_.end(); ++iter) {
+    pref_service_->RemoveSyncedPrefObserver(iter->first, this);
+  }
+  observers_.clear();
+}
+
+bool SyncedPrefChangeRegistrar::IsObserved(const char* path) const {
+  return observers_.find(path) != observers_.end();
+}
+
+void SyncedPrefChangeRegistrar::OnSyncedPrefChanged(const std::string& path,
+    bool from_sync) {
+  ObserverMap::const_iterator iter = observers_.find(path);
+  if (iter == observers_.end())
+    return;
+  iter->second.Run(path, from_sync);
+}