diff --git a/buffet/manager.cc b/buffet/manager.cc
index 78a0a8c..96319c0 100644
--- a/buffet/manager.cc
+++ b/buffet/manager.cc
@@ -137,17 +137,7 @@
 void Manager::UpdateState(DBusMethodResponse<> response,
                           const chromeos::VariantDictionary& property_set) {
   chromeos::ErrorPtr error;
-  base::Time timestamp = base::Time::Now();
-  bool all_success = true;
-  for (const auto& pair : property_set) {
-    if (!state_manager_->SetPropertyValue(pair.first, pair.second, timestamp,
-                                          &error)) {
-      // Remember that an error occurred but keep going and update the rest of
-      // the properties if possible.
-      all_success = false;
-    }
-  }
-  if (!all_success)
+  if (!state_manager_->SetProperties(property_set, &error))
     response->ReplyWithError(error.get());
   else
     response->Return();
diff --git a/buffet/states/state_manager.cc b/buffet/states/state_manager.cc
index 827cd7f..57330f4 100644
--- a/buffet/states/state_manager.cc
+++ b/buffet/states/state_manager.cc
@@ -30,6 +30,11 @@
   CHECK(state_change_queue_) << "State change queue not specified";
 }
 
+void StateManager::AddOnChangedCallback(const base::Closure& callback) {
+  on_changed_.push_back(callback);
+  callback.Run();  // Force to read current state.
+}
+
 void StateManager::Startup() {
   LOG(INFO) << "Initializing StateManager.";
 
@@ -88,6 +93,9 @@
                          firmware_version,
                          base::Time::Now(),
                          nullptr));
+
+  for (const auto& cb : on_changed_)
+    cb.Run();
 }
 
 std::unique_ptr<base::DictionaryValue> StateManager::GetStateValuesAsJson(
@@ -104,6 +112,23 @@
   return dict;
 }
 
+bool StateManager::SetProperties(
+    const chromeos::VariantDictionary& property_set,
+    chromeos::ErrorPtr* error) {
+  base::Time timestamp = base::Time::Now();
+  bool all_success = true;
+  for (const auto& pair : property_set) {
+    if (!SetPropertyValue(pair.first, pair.second, timestamp, error)) {
+      // Remember that an error occurred but keep going and update the rest of
+      // the properties if possible.
+      all_success = false;
+    }
+  }
+  for (const auto& cb : on_changed_)
+    cb.Run();
+  return all_success;
+}
+
 bool StateManager::SetPropertyValue(const std::string& full_property_name,
                                     const chromeos::Any& value,
                                     const base::Time& timestamp,
diff --git a/buffet/states/state_manager.h b/buffet/states/state_manager.h
index 53695e2..cf2c60a 100644
--- a/buffet/states/state_manager.h
+++ b/buffet/states/state_manager.h
@@ -11,6 +11,7 @@
 #include <string>
 #include <vector>
 
+#include <base/callback.h>
 #include <base/macros.h>
 #include <chromeos/errors/error.h>
 #include <chromeos/variant_dictionary.h>
@@ -33,6 +34,8 @@
  public:
   explicit StateManager(StateChangeQueueInterface* state_change_queue);
 
+  void AddOnChangedCallback(const base::Closure& callback);
+
   // Initializes the state manager and load device state fragments.
   // Called by Buffet daemon at startup.
   void Startup();
@@ -42,12 +45,9 @@
   std::unique_ptr<base::DictionaryValue> GetStateValuesAsJson(
       chromeos::ErrorPtr* error) const;
 
-  // Updates a single property value. |full_property_name| must be the full
-  // name of the property to update in format "package.property".
-  bool SetPropertyValue(const std::string& full_property_name,
-                        const chromeos::Any& value,
-                        const base::Time& timestamp,
-                        chromeos::ErrorPtr* error);
+  // Updates a multiple property values.
+  bool SetProperties(const chromeos::VariantDictionary& property_set,
+                     chromeos::ErrorPtr* error);
 
   // Returns all the categories the state properties are registered from.
   // As with GCD command handling, the category normally represent a device
@@ -61,6 +61,15 @@
   std::vector<StateChange> GetAndClearRecordedStateChanges();
 
  private:
+  friend class StateManagerTest;
+
+  // Updates a single property value. |full_property_name| must be the full
+  // name of the property to update in format "package.property".
+  bool SetPropertyValue(const std::string& full_property_name,
+                        const chromeos::Any& value,
+                        const base::Time& timestamp,
+                        chromeos::ErrorPtr* error);
+
   // Loads a device state fragment from a JSON object. |category| represents
   // a device daemon providing the state fragment or empty string for the
   // base state fragment.
@@ -96,7 +105,8 @@
   std::map<std::string, std::unique_ptr<StatePackage>> packages_;
   std::set<std::string> categories_;
 
-  friend class StateManagerTest;
+  std::vector<base::Closure> on_changed_;
+
   DISALLOW_COPY_AND_ASSIGN(StateManager);
 };
 
diff --git a/buffet/states/state_manager_unittest.cc b/buffet/states/state_manager_unittest.cc
index d71ebb6..50e6a5f 100644
--- a/buffet/states/state_manager_unittest.cc
+++ b/buffet/states/state_manager_unittest.cc
@@ -7,6 +7,7 @@
 #include <cstdlib>  // for abs().
 #include <vector>
 
+#include <base/bind.h>
 #include <base/values.h>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
@@ -56,6 +57,11 @@
     EXPECT_CALL(mock_state_change_queue_, GetAndClearRecordedStateChanges())
         .Times(0);
     mgr_.reset(new StateManager(&mock_state_change_queue_));
+
+    EXPECT_CALL(*this, OnStateChanged()).Times(1);
+    mgr_->AddOnChangedCallback(
+        base::Bind(&StateManagerTest::OnStateChanged, base::Unretained(this)));
+
     LoadStateDefinition(GetTestSchema().get(), "default", nullptr);
     ASSERT_TRUE(mgr_->LoadStateDefaults(*GetTestValues().get(), nullptr));
   }
@@ -67,6 +73,15 @@
     ASSERT_TRUE(mgr_->LoadStateDefinition(*json, category, error));
   }
 
+  bool SetPropertyValue(const std::string& name,
+                        const chromeos::Any& value,
+                        chromeos::ErrorPtr* error) {
+    return mgr_->SetPropertyValue(name, value, timestamp_, error);
+  }
+
+  MOCK_CONST_METHOD0(OnStateChanged, void());
+
+  base::Time timestamp_{base::Time::Now()};
   std::unique_ptr<StateManager> mgr_;
   MockStateChangeQueueInterface mock_state_change_queue_;
 };
@@ -120,12 +135,11 @@
   native_types::Object expected_prop_set{
       {"terminator.target", unittests::make_string_prop_value("John Connor")},
   };
-  base::Time timestamp = base::Time::Now();
   EXPECT_CALL(mock_state_change_queue_,
-              NotifyPropertiesUpdated(timestamp, expected_prop_set))
+              NotifyPropertiesUpdated(timestamp_, expected_prop_set))
       .WillOnce(Return(true));
-  ASSERT_TRUE(mgr_->SetPropertyValue(
-      "terminator.target", std::string{"John Connor"}, timestamp, nullptr));
+  ASSERT_TRUE(SetPropertyValue("terminator.target", std::string{"John Connor"},
+                               nullptr));
   auto expected = R"({
     'base': {
       'manufacturer': 'Skynet',
@@ -140,7 +154,7 @@
 
 TEST_F(StateManagerTest, SetPropertyValue_Error_NoName) {
   chromeos::ErrorPtr error;
-  ASSERT_FALSE(mgr_->SetPropertyValue("", int{0}, base::Time::Now(), &error));
+  ASSERT_FALSE(SetPropertyValue("", int{0}, &error));
   EXPECT_EQ(errors::state::kDomain, error->GetDomain());
   EXPECT_EQ(errors::state::kPropertyNameMissing, error->GetCode());
   EXPECT_EQ("Property name is missing", error->GetMessage());
@@ -148,8 +162,7 @@
 
 TEST_F(StateManagerTest, SetPropertyValue_Error_NoPackage) {
   chromeos::ErrorPtr error;
-  ASSERT_FALSE(
-      mgr_->SetPropertyValue("target", int{0}, base::Time::Now(), &error));
+  ASSERT_FALSE(SetPropertyValue("target", int{0}, &error));
   EXPECT_EQ(errors::state::kDomain, error->GetDomain());
   EXPECT_EQ(errors::state::kPackageNameMissing, error->GetCode());
   EXPECT_EQ("Package name is missing in the property name",
@@ -158,8 +171,7 @@
 
 TEST_F(StateManagerTest, SetPropertyValue_Error_UnknownPackage) {
   chromeos::ErrorPtr error;
-  ASSERT_FALSE(
-      mgr_->SetPropertyValue("power.level", int{0}, base::Time::Now(), &error));
+  ASSERT_FALSE(SetPropertyValue("power.level", int{0}, &error));
   EXPECT_EQ(errors::state::kDomain, error->GetDomain());
   EXPECT_EQ(errors::state::kPropertyNotDefined, error->GetCode());
   EXPECT_EQ("Unknown state property package 'power'", error->GetMessage());
@@ -167,22 +179,20 @@
 
 TEST_F(StateManagerTest, SetPropertyValue_Error_UnknownProperty) {
   chromeos::ErrorPtr error;
-  ASSERT_FALSE(
-      mgr_->SetPropertyValue("base.level", int{0}, base::Time::Now(), &error));
+  ASSERT_FALSE(SetPropertyValue("base.level", int{0}, &error));
   EXPECT_EQ(errors::state::kDomain, error->GetDomain());
   EXPECT_EQ(errors::state::kPropertyNotDefined, error->GetCode());
   EXPECT_EQ("State property 'base.level' is not defined", error->GetMessage());
 }
 
 TEST_F(StateManagerTest, GetAndClearRecordedStateChanges) {
-  base::Time timestamp = base::Time::Now();
-  EXPECT_CALL(mock_state_change_queue_, NotifyPropertiesUpdated(timestamp, _))
+  EXPECT_CALL(mock_state_change_queue_, NotifyPropertiesUpdated(timestamp_, _))
       .WillOnce(Return(true));
-  ASSERT_TRUE(mgr_->SetPropertyValue(
-      "terminator.target", std::string{"John Connor"}, timestamp, nullptr));
+  ASSERT_TRUE(SetPropertyValue("terminator.target", std::string{"John Connor"},
+                               nullptr));
   std::vector<StateChange> expected_val;
   expected_val.emplace_back(
-      timestamp,
+      timestamp_,
       native_types::Object{{"terminator.target",
                             unittests::make_string_prop_value("John Connor")}});
   EXPECT_CALL(mock_state_change_queue_, GetAndClearRecordedStateChanges())
@@ -194,4 +204,28 @@
             changes.back().changed_properties);
 }
 
+TEST_F(StateManagerTest, SetProperties) {
+  native_types::Object expected_prop_set{
+      {"base.manufacturer", unittests::make_string_prop_value("No Name")},
+  };
+  EXPECT_CALL(mock_state_change_queue_,
+              NotifyPropertiesUpdated(_, expected_prop_set))
+      .WillOnce(Return(true));
+
+  EXPECT_CALL(*this, OnStateChanged()).Times(1);
+  ASSERT_TRUE(mgr_->SetProperties(
+      {{"base.manufacturer", std::string("No Name")}}, nullptr));
+
+  auto expected = R"({
+    'base': {
+      'manufacturer': 'No Name',
+      'serialNumber': 'T1000'
+    },
+    'terminator': {
+      'target': ''
+    }
+  })";
+  EXPECT_JSON_EQ(expected, *mgr_->GetStateValuesAsJson(nullptr));
+}
+
 }  // namespace buffet