nfc: Move object proxy update logic based on properties to DBusObjectMap.

Added nfc_client_helpers::DBusObjectMap::UpdateObjects. This simplifies the NFC
client classes in the way they keep track of added and removed remote objects
based on D-Bus properties that they keep track of. This also reduces the size
of changes that need to be made once we transition to neard 0.14, which will
use DBus.ObjectManager.

BUG=304979

Review URL: https://codereview.chromium.org/45333006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232421 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 176 insertions, 206 deletions

diff --git a/chromeos/dbus/nfc_adapter_client.cc b/chromeos/dbus/nfc_adapter_client.cc
index 040db2a..476aaf2 100644
--- a/chromeos/dbus/nfc_adapter_client.cc
+++ b/chromeos/dbus/nfc_adapter_client.cc
@@ -43,8 +43,7 @@ class NfcAdapterClientImpl
       public nfc_client_helpers::DBusObjectMap::Delegate {
  public:
   explicit NfcAdapterClientImpl(NfcManagerClient* manager_client)
-      : initial_adapters_received_(false),
-        bus_(NULL),
+      : bus_(NULL),
         manager_client_(manager_client),
         weak_ptr_factory_(this) {
     DCHECK(manager_client);
@@ -138,51 +137,23 @@ class NfcAdapterClientImpl
 
  private:
   // NfcManagerClient::Observer override.
-  virtual void AdapterAdded(const dbus::ObjectPath& object_path) OVERRIDE {
-    VLOG(1) << "AdapterAdded: " << object_path.value();
-    // Initialize the object proxy here, so that observers can start receiving
-    // notifications for it and it is cached for reuse. Note that, even if we
-    // miss this signal, a proxy will be created on demand for any object paths
-    // that are passed to the public methods later.
-    object_map_->AddObject(object_path);
-    FOR_EACH_OBSERVER(NfcAdapterClient::Observer, observers_,
-                      AdapterAdded(object_path));
-  }
-
-  // NfcManagerClient::Observer override.
-  virtual void AdapterRemoved(const dbus::ObjectPath& object_path) OVERRIDE {
-    VLOG(1) << "AdapterRemoved: " << object_path.value();
-    // Remove the object proxy, as we know that the adapter no longer exists.
-    // Note that this doesn't prevent a client from recreating a proxy for an
-    // object path that is no longer valid, as proxies are created on demand as
-    // necessary by the public methods.
-    object_map_->RemoveObject(object_path);
-    FOR_EACH_OBSERVER(NfcAdapterClient::Observer, observers_,
-                      AdapterRemoved(object_path));
-  }
-
-  // NfcManagerClient::Observer override.
   virtual void ManagerPropertyChanged(
       const std::string& property_name) OVERRIDE {
+    // Update the adapter proxies.
+    DCHECK(manager_client_);
     NfcManagerClient::Properties* manager_properties =
         manager_client_->GetProperties();
-    if (!initial_adapters_received_ &&
-        property_name == manager_properties->adapters.name()) {
-      initial_adapters_received_ = true;
-      VLOG(1) << "Initial set of adapters received.";
-      // Create proxies for all adapters that are known to the manager, so that
-      // observers can start getting notified for any signals emitted by
-      // adapters. We use the PropertyChanged signal from manager only to
-      // create proxies for the initial fetch. We rely on the AdapterAdded and
-      // AdapterRemoved signals after that.
-      std::vector<dbus::ObjectPath> adapters =
-          manager_properties->adapters.value();
-      for (std::vector<dbus::ObjectPath>::iterator iter = adapters.begin();
-           iter != adapters.end(); ++iter) {
-        VLOG(1) << "Creating proxy for: " << iter->value();
-        object_map_->AddObject(*iter);
-      }
-    }
+
+    // Ignore changes to properties other than "Adapters".
+    if (property_name != manager_properties->adapters.name())
+      return;
+
+    VLOG(1) << "NFC adapters changed.";
+
+    // Update the known adapters.
+    const std::vector<dbus::ObjectPath>& received_adapters =
+        manager_properties->adapters.value();
+    object_map_->UpdateObjects(received_adapters);
   }
 
   // nfc_client_helpers::DBusObjectMap::Delegate override.
@@ -195,6 +166,17 @@ class NfcAdapterClientImpl
                    object_proxy->object_path()));
   }
 
+  // nfc_client_helpers::DBusObjectMap::Delegate override.
+  virtual void ObjectAdded(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcAdapterClient::Observer, observers_,
+                      AdapterAdded(object_path));
+  }
+
+  virtual void ObjectRemoved(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcAdapterClient::Observer, observers_,
+                      AdapterRemoved(object_path));
+  }
+
   // Called by NfcPropertySet when a property value is changed, either by
   // result of a signal or response to a GetAll() or Get() call.
   void OnPropertyChanged(const dbus::ObjectPath& object_path,
@@ -205,11 +187,6 @@ class NfcAdapterClientImpl
                       AdapterPropertyChanged(object_path, property_name));
   }
 
-  // This variable stores whether or not we have ever been notified of
-  // ManagerPropertiesChanged. This is used to bootstrap adapter proxies
-  // after receiving the initial set of properties from the NFC manager.
-  bool initial_adapters_received_;
-
   // We maintain a pointer to the bus to be able to request proxies for
   // new NFC adapters that appear.
   dbus::Bus* bus_;
diff --git a/chromeos/dbus/nfc_client_helpers.cc b/chromeos/dbus/nfc_client_helpers.cc
index 51889e81..0e5add2 100644
--- a/chromeos/dbus/nfc_client_helpers.cc
+++ b/chromeos/dbus/nfc_client_helpers.cc
@@ -4,6 +4,8 @@
 
 #include "chromeos/dbus/nfc_client_helpers.h"
 
+#include "base/stl_util.h"
+
 namespace chromeos {
 namespace nfc_client_helpers {
 
@@ -61,12 +63,50 @@ NfcPropertySet* DBusObjectMap::GetObjectProperties(
   return GetObjectPropertyPair(object_path).second;
 }
 
+void DBusObjectMap::UpdateObjects(
+    const std::vector<dbus::ObjectPath>& object_paths) {
+  // This set is used to query if an object path was removed, while updating
+  // the removed paths below. The iterator is used as a hint to accelerate
+  // insertion.
+  std::set<dbus::ObjectPath> object_path_set;
+  std::set<dbus::ObjectPath>::iterator object_path_set_iter =
+      object_path_set.begin();
+
+  // Add all objects.
+  for (std::vector<dbus::ObjectPath>::const_iterator iter =
+          object_paths.begin();
+       iter != object_paths.end(); ++iter) {
+    const dbus::ObjectPath &object_path = *iter;
+    AddObject(object_path);
+    // Neard usually returns object paths in ascending order. Give a hint here
+    // to make insertion amortized constant.
+    object_path_set_iter =
+        object_path_set.insert(object_path_set_iter, object_path);
+  }
+
+  // Remove all objects that are not in |object_paths|.
+  ObjectMap::const_iterator iter = object_map_.begin();
+  while (iter != object_map_.end()) {
+    // Make a copy here, as the iterator will be invalidated by
+    // DBusObjectMap::RemoveObject below, but |object_path| is needed to
+    // notify observers right after. We want to make sure that we notify
+    // the observers AFTER we remove the object, so that method calls
+    // to the removed object paths in observer implementations fail
+    // gracefully.
+    dbus::ObjectPath object_path = iter->first;
+    ++iter;
+    if (!ContainsKey(object_path_set, object_path))
+      RemoveObject(object_path);
+  }
+}
+
 bool DBusObjectMap::AddObject(const dbus::ObjectPath& object_path) {
   ObjectMap::iterator iter = object_map_.find(object_path);
   if (iter != object_map_.end())
     return false;
 
   DCHECK(bus_);
+  DCHECK(delegate_);
   dbus::ObjectProxy* object_proxy = bus_->GetObjectProxy(service_name_,
                                                          object_path);
 
@@ -74,15 +114,17 @@ bool DBusObjectMap::AddObject(const dbus::ObjectPath& object_path) {
   NfcPropertySet* properties = delegate_->CreateProperties(object_proxy);
   properties->ConnectSignals();
   properties->GetAll();
-  VLOG(1) << "Created proxy for object with Path: " << object_path.value()
-          << ", Service: " << service_name_;
   ObjectPropertyPair object = std::make_pair(object_proxy, properties);
   object_map_[object_path] = object;
+  VLOG(1) << "Created proxy for object with Path: " << object_path.value()
+          << ", Service: " << service_name_;
+  delegate_->ObjectAdded(object_path);
   return true;
 }
 
 void DBusObjectMap::RemoveObject(const dbus::ObjectPath& object_path) {
   DCHECK(bus_);
+  DCHECK(delegate_);
   ObjectMap::iterator iter = object_map_.find(object_path);
   if (iter == object_map_.end())
     return;
@@ -90,6 +132,9 @@ void DBusObjectMap::RemoveObject(const dbus::ObjectPath& object_path) {
   ObjectPropertyPair pair = iter->second;
   CleanUpObjectPropertyPair(pair);
   object_map_.erase(iter);
+  VLOG(1) << "Object proxy removed for object path: "
+          << object_path.value();
+  delegate_->ObjectRemoved(object_path);
 }
 
 DBusObjectMap::ObjectPropertyPair DBusObjectMap::GetObjectPropertyPair(
diff --git a/chromeos/dbus/nfc_client_helpers.h b/chromeos/dbus/nfc_client_helpers.h
index ed344db..2d579f2c 100644
--- a/chromeos/dbus/nfc_client_helpers.h
+++ b/chromeos/dbus/nfc_client_helpers.h
@@ -62,10 +62,15 @@ class CHROMEOS_EXPORT DBusObjectMap {
     // signals and update the properties.
     virtual NfcPropertySet* CreateProperties(
         dbus::ObjectProxy* object_proxy) = 0;
-  };
 
-  typedef std::pair<dbus::ObjectProxy*, NfcPropertySet*> ObjectPropertyPair;
-  typedef std::map<dbus::ObjectPath, ObjectPropertyPair> ObjectMap;
+    // Notifies the delegate that an object was added with object path
+    // |object_path|.
+    virtual void ObjectAdded(const dbus::ObjectPath& object_path) {}
+
+    // Notifies the delegate that an object was removed with object path
+    // |object_path|.
+    virtual void ObjectRemoved(const dbus::ObjectPath& object_path) {}
+  };
 
   // Constructor takes in the D-Bus service name the proxies belong to and
   // the delegate which will be used to construct properties structures.
@@ -85,6 +90,11 @@ class CHROMEOS_EXPORT DBusObjectMap {
   // returns NULL.
   NfcPropertySet* GetObjectProperties(const dbus::ObjectPath& object_path);
 
+  // Updates the object proxies from the given list of object paths
+  // |object_paths|. It notifies the delegate of each added and removed object
+  // via |Delegate::ObjectAdded| and |Delegate::ObjectRemoved|.
+  void UpdateObjects(const std::vector<dbus::ObjectPath>& object_paths);
+
   // Creates and stores an object proxy and properties structure for a remote
   // object with object path |object_path|. If an object proxy was already
   // created, this operation returns false; returns true otherwise.
@@ -94,10 +104,10 @@ class CHROMEOS_EXPORT DBusObjectMap {
   // remote object with object path |object_path|.
   void RemoveObject(const dbus::ObjectPath& object_path);
 
-  // Returns the underlying map.
-  const ObjectMap& object_map() const { return object_map_; }
-
  private:
+  typedef std::pair<dbus::ObjectProxy*, NfcPropertySet*> ObjectPropertyPair;
+  typedef std::map<dbus::ObjectPath, ObjectPropertyPair> ObjectMap;
+
   // Returns an instance of ObjectPropertyPair by looking up |object_path| in
   // |object_map_|. If no entry is found, returns an instance that contains
   // NULL pointers.
diff --git a/chromeos/dbus/nfc_client_unittest.cc b/chromeos/dbus/nfc_client_unittest.cc
index 7327d9e..512b7de 100644
--- a/chromeos/dbus/nfc_client_unittest.cc
+++ b/chromeos/dbus/nfc_client_unittest.cc
@@ -53,20 +53,16 @@ class MockNfcAdapterObserver : public NfcAdapterClient::Observer {
 
 class MockNfcDeviceObserver : public NfcDeviceClient::Observer {
  public:
-  MOCK_METHOD2(DeviceFound, void(const dbus::ObjectPath&,
-                                 const dbus::ObjectPath&));
-  MOCK_METHOD2(DeviceLost, void(const dbus::ObjectPath&,
-                                const dbus::ObjectPath&));
+  MOCK_METHOD1(DeviceFound, void(const dbus::ObjectPath&));
+  MOCK_METHOD1(DeviceLost, void(const dbus::ObjectPath&));
   MOCK_METHOD2(DevicePropertyChanged, void(const dbus::ObjectPath&,
                                            const std::string&));
 };
 
 class MockNfcTagObserver : public NfcTagClient::Observer {
  public:
-  MOCK_METHOD2(TagFound, void(const dbus::ObjectPath&,
-                              const dbus::ObjectPath&));
-  MOCK_METHOD2(TagLost, void(const dbus::ObjectPath&,
-                             const dbus::ObjectPath&));
+  MOCK_METHOD1(TagFound, void(const dbus::ObjectPath&));
+  MOCK_METHOD1(TagLost, void(const dbus::ObjectPath&));
   MOCK_METHOD2(TagPropertyChanged, void(const dbus::ObjectPath&,
                                         const std::string&));
 };
@@ -189,28 +185,19 @@ class NfcClientTest : public testing::Test {
     mock_bus_->ShutdownAndBlock();
   }
 
-  void SimulateAdapterAdded(const dbus::ObjectPath& object_path) {
-    EXPECT_CALL(mock_manager_observer_, AdapterAdded(object_path));
-    EXPECT_CALL(mock_adapter_observer_, AdapterAdded(object_path));
-    dbus::Signal signal(nfc_manager::kNfcManagerInterface,
-                        nfc_manager::kAdapterAddedSignal);
-    dbus::MessageWriter writer(&signal);
-    writer.AppendObjectPath(object_path);
-    ASSERT_FALSE(manager_adapter_added_signal_callback_.is_null());
-    manager_adapter_added_signal_callback_.Run(&signal);
-  }
-
-  void SimulateAdapterRemoved(const dbus::ObjectPath& object_path) {
-    EXPECT_CALL(mock_manager_observer_, AdapterRemoved(object_path));
-    EXPECT_CALL(mock_adapter_observer_, AdapterRemoved(object_path));
-    dbus::Signal signal(nfc_manager::kNfcManagerInterface,
-                        nfc_manager::kAdapterRemovedSignal);
-    dbus::MessageWriter writer(&signal);
-    writer.AppendObjectPath(object_path);
-    ASSERT_FALSE(manager_adapter_removed_signal_callback_.is_null());
-    manager_adapter_removed_signal_callback_.Run(&signal);
+  void SimulateAdaptersChanged(
+      const std::vector<dbus::ObjectPath>& adapter_paths) {
+    NfcManagerClient::Properties* properties =
+        manager_client_->GetProperties();
+    ASSERT_TRUE(properties);
+    EXPECT_CALL(mock_manager_observer_,
+                ManagerPropertyChanged(nfc_manager::kAdaptersProperty));
+    SendArrayPropertyChangedSignal(
+        properties,
+        nfc_manager::kNfcManagerInterface,
+        nfc_manager::kAdaptersProperty,
+        adapter_paths);
     Mock::VerifyAndClearExpectations(&mock_manager_observer_);
-    Mock::VerifyAndClearExpectations(&mock_adapter_observer_);
   }
 
   void SimulateTagsChanged(const std::vector<dbus::ObjectPath>& tag_paths,
@@ -328,7 +315,11 @@ TEST_F(NfcClientTest, AdaptersAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(this);
 
   // Add adapter 0.
-  SimulateAdapterAdded(dbus::ObjectPath(kTestAdapterPath0));
+  std::vector<dbus::ObjectPath> adapter_paths;
+  adapter_paths.push_back(dbus::ObjectPath(kTestAdapterPath0));
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterAdded(dbus::ObjectPath(kTestAdapterPath0)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Invoking methods should succeed on adapter 0 but fail on adapter 1.
   EXPECT_CALL(*mock_adapter0_proxy_, CallMethodWithErrorCallback(_, _, _, _));
@@ -351,7 +342,10 @@ TEST_F(NfcClientTest, AdaptersAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(&mock_adapter1_proxy_);
 
   // Add adapter 1.
-  SimulateAdapterAdded(dbus::ObjectPath(kTestAdapterPath1));
+  adapter_paths.push_back(dbus::ObjectPath(kTestAdapterPath1));
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterAdded(dbus::ObjectPath(kTestAdapterPath1)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Invoking methods should succeed on both adapters.
   EXPECT_CALL(*mock_adapter0_proxy_, CallMethodWithErrorCallback(_, _, _, _));
@@ -370,7 +364,10 @@ TEST_F(NfcClientTest, AdaptersAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(&mock_adapter1_proxy_);
 
   // Remove adapter 0.
-  SimulateAdapterRemoved(dbus::ObjectPath(kTestAdapterPath0));
+  adapter_paths.erase(adapter_paths.begin());
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterRemoved(dbus::ObjectPath(kTestAdapterPath0)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Invoking methods should succeed on adapter 1 but fail on adapter 0.
   EXPECT_CALL(*this,
@@ -394,7 +391,10 @@ TEST_F(NfcClientTest, AdaptersAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(&mock_adapter1_proxy_);
 
   // Remove adapter 1.
-  SimulateAdapterRemoved(dbus::ObjectPath(kTestAdapterPath1));
+  adapter_paths.clear();
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterRemoved(dbus::ObjectPath(kTestAdapterPath1)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Invoking methods should fail on both adapters.
   EXPECT_CALL(*this,
@@ -433,14 +433,17 @@ TEST_F(NfcClientTest, TagsAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(this);
 
   // Add adapter 0.
-  SimulateAdapterAdded(dbus::ObjectPath(kTestAdapterPath0));
+  std::vector<dbus::ObjectPath> adapter_paths;
+  adapter_paths.push_back(dbus::ObjectPath(kTestAdapterPath0));
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterAdded(dbus::ObjectPath(kTestAdapterPath0)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Add tag 0.
   std::vector<dbus::ObjectPath> tag_paths;
   tag_paths.push_back(dbus::ObjectPath(kTestTagPath0));
   EXPECT_CALL(mock_tag_observer_,
-              TagFound(dbus::ObjectPath(kTestTagPath0),
-                       dbus::ObjectPath(kTestAdapterPath0)));
+              TagFound(dbus::ObjectPath(kTestTagPath0)));
   SimulateTagsChanged(tag_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_tag_observer_);
 
@@ -467,8 +470,7 @@ TEST_F(NfcClientTest, TagsAddedAndRemoved) {
   // Add tag 1.
   tag_paths.push_back(dbus::ObjectPath(kTestTagPath1));
   EXPECT_CALL(mock_tag_observer_,
-              TagFound(dbus::ObjectPath(kTestTagPath1),
-                       dbus::ObjectPath(kTestAdapterPath0)));
+              TagFound(dbus::ObjectPath(kTestTagPath1)));
   SimulateTagsChanged(tag_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_tag_observer_);
 
@@ -491,8 +493,7 @@ TEST_F(NfcClientTest, TagsAddedAndRemoved) {
   // Remove tag 0.
   tag_paths.erase(tag_paths.begin());
   EXPECT_CALL(mock_tag_observer_,
-              TagLost(dbus::ObjectPath(kTestTagPath0),
-                      dbus::ObjectPath(kTestAdapterPath0)));
+              TagLost(dbus::ObjectPath(kTestTagPath0)));
   SimulateTagsChanged(tag_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_tag_observer_);
 
@@ -519,8 +520,7 @@ TEST_F(NfcClientTest, TagsAddedAndRemoved) {
   // Remove tag 1.
   tag_paths.clear();
   EXPECT_CALL(mock_tag_observer_,
-              TagLost(dbus::ObjectPath(kTestTagPath1),
-                      dbus::ObjectPath(kTestAdapterPath0)));
+              TagLost(dbus::ObjectPath(kTestTagPath1)));
   SimulateTagsChanged(tag_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_tag_observer_);
 
@@ -561,14 +561,17 @@ TEST_F(NfcClientTest, DevicesAddedAndRemoved) {
   Mock::VerifyAndClearExpectations(this);
 
   // Add adapter 0.
-  SimulateAdapterAdded(dbus::ObjectPath(kTestAdapterPath0));
+  std::vector<dbus::ObjectPath> adapter_paths;
+  adapter_paths.push_back(dbus::ObjectPath(kTestAdapterPath0));
+  EXPECT_CALL(mock_adapter_observer_,
+              AdapterAdded(dbus::ObjectPath(kTestAdapterPath0)));
+  SimulateAdaptersChanged(adapter_paths);
 
   // Add device 0.
   std::vector<dbus::ObjectPath> device_paths;
   device_paths.push_back(dbus::ObjectPath(kTestDevicePath0));
   EXPECT_CALL(mock_device_observer_,
-              DeviceFound(dbus::ObjectPath(kTestDevicePath0),
-                          dbus::ObjectPath(kTestAdapterPath0)));
+              DeviceFound(dbus::ObjectPath(kTestDevicePath0)));
   SimulateDevicesChanged(device_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_device_observer_);
 
@@ -595,8 +598,7 @@ TEST_F(NfcClientTest, DevicesAddedAndRemoved) {
   // Add device 1.
   device_paths.push_back(dbus::ObjectPath(kTestDevicePath1));
   EXPECT_CALL(mock_device_observer_,
-              DeviceFound(dbus::ObjectPath(kTestDevicePath1),
-                          dbus::ObjectPath(kTestAdapterPath0)));
+              DeviceFound(dbus::ObjectPath(kTestDevicePath1)));
   SimulateDevicesChanged(device_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_device_observer_);
 
@@ -619,8 +621,7 @@ TEST_F(NfcClientTest, DevicesAddedAndRemoved) {
   // Remove device 0.
   device_paths.erase(device_paths.begin());
   EXPECT_CALL(mock_device_observer_,
-              DeviceLost(dbus::ObjectPath(kTestDevicePath0),
-                         dbus::ObjectPath(kTestAdapterPath0)));
+              DeviceLost(dbus::ObjectPath(kTestDevicePath0)));
   SimulateDevicesChanged(device_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_device_observer_);
 
@@ -647,8 +648,7 @@ TEST_F(NfcClientTest, DevicesAddedAndRemoved) {
   // Remove device 1.
   device_paths.clear();
   EXPECT_CALL(mock_device_observer_,
-              DeviceLost(dbus::ObjectPath(kTestDevicePath1),
-                         dbus::ObjectPath(kTestAdapterPath0)));
+              DeviceLost(dbus::ObjectPath(kTestDevicePath1)));
   SimulateDevicesChanged(device_paths, dbus::ObjectPath(kTestAdapterPath0));
   Mock::VerifyAndClearExpectations(&mock_device_observer_);
 
diff --git a/chromeos/dbus/nfc_device_client.cc b/chromeos/dbus/nfc_device_client.cc
index 83076d2..c1a212a 100644
--- a/chromeos/dbus/nfc_device_client.cc
+++ b/chromeos/dbus/nfc_device_client.cc
@@ -9,7 +9,6 @@
 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
-#include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "chromeos/dbus/fake_nfc_device_client.h"
 #include "chromeos/dbus/nfc_adapter_client.h"
@@ -21,12 +20,6 @@ using chromeos::nfc_client_helpers::DBusObjectMap;
 
 namespace chromeos {
 
-namespace {
-
-typedef std::vector<dbus::ObjectPath> ObjectPathVector;
-
-}  // namespace
-
 NfcDeviceClient::Properties::Properties(
     dbus::ObjectProxy* object_proxy,
     const PropertyChangedCallback& callback)
@@ -150,41 +143,10 @@ class NfcDeviceClientImpl : public NfcDeviceClient,
 
     VLOG(1) << "NFC devices changed.";
 
-    // Add all the new devices.
-    const ObjectPathVector& received_devices =
+    // Update the known devices.
+    const std::vector<dbus::ObjectPath>& received_devices =
         adapter_properties->devices.value();
-    for (ObjectPathVector::const_iterator iter = received_devices.begin();
-         iter != received_devices.end(); ++iter) {
-      const dbus::ObjectPath &device_path = *iter;
-      if (object_map_->AddObject(device_path)) {
-        VLOG(1) << "Found NFC device: " << device_path.value();
-        FOR_EACH_OBSERVER(NfcDeviceClient::Observer, observers_,
-                          DeviceFound(device_path, object_path));
-      }
-    }
-
-    // Remove all devices that were lost.
-    const DBusObjectMap::ObjectMap& known_devices =
-        object_map_->object_map();
-    std::set<dbus::ObjectPath> devices_set(received_devices.begin(),
-                                           received_devices.end());
-    DBusObjectMap::ObjectMap::const_iterator iter = known_devices.begin();
-    while (iter != known_devices.end()) {
-      // Make a copy here, as the iterator will be invalidated by
-      // DBusObjectMap::RemoveObject below, but |device_path| is needed to
-      // notify observers right after. We want to make sure that we notify
-      // the observers AFTER we remove the object, so that method calls
-      // to the removed object paths in observer implementations fail
-      // gracefully.
-      dbus::ObjectPath device_path = iter->first;
-      ++iter;
-      if (!ContainsKey(devices_set, device_path)) {
-        VLOG(1) << "Lost NFC device: " << device_path.value();
-        object_map_->RemoveObject(device_path);
-        FOR_EACH_OBSERVER(NfcDeviceClient::Observer, observers_,
-                          DeviceLost(device_path, object_path));
-      }
-    }
+    object_map_->UpdateObjects(received_devices);
   }
 
   // nfc_client_helpers::DBusObjectMap::Delegate override.
@@ -197,6 +159,17 @@ class NfcDeviceClientImpl : public NfcDeviceClient,
                    object_proxy->object_path()));
   }
 
+  // nfc_client_helpers::DBusObjectMap::Delegate override.
+  virtual void ObjectAdded(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcDeviceClient::Observer, observers_,
+                      DeviceFound(object_path));
+  }
+
+  virtual void ObjectRemoved(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcDeviceClient::Observer, observers_,
+                      DeviceLost(object_path));
+  }
+
   // Called by NfcPropertySet when a property value is changed, either by
   // result of a signal or response to a GetAll() or Get() call.
   void OnPropertyChanged(const dbus::ObjectPath& object_path,
diff --git a/chromeos/dbus/nfc_device_client.h b/chromeos/dbus/nfc_device_client.h
index bbabf7e..314a70a 100644
--- a/chromeos/dbus/nfc_device_client.h
+++ b/chromeos/dbus/nfc_device_client.h
@@ -23,7 +23,7 @@ namespace chromeos {
 class NfcAdapterClient;
 
 // NfcDeviceClient is used to communicate with objects representing remote NFC
-// adapters that can be communicated with.
+// devices that can be communicated with.
 class CHROMEOS_EXPORT NfcDeviceClient : public DBusClient {
  public:
   // Structure of properties associated with an NFC device.
@@ -42,16 +42,12 @@ class CHROMEOS_EXPORT NfcDeviceClient : public DBusClient {
     virtual ~Observer() {}
 
     // Called when a remote NFC device with the object |object_path| is added
-    // to the set of known devices associated with the adapter with object path
-    // |adapter_path|.
-    virtual void DeviceFound(const dbus::ObjectPath& object_path,
-                             const dbus::ObjectPath& adapter_path) {}
+    // to the set of known devices.
+    virtual void DeviceFound(const dbus::ObjectPath& object_path) {}
 
     // Called when a remote NFC device with the object path |object_path| is
-    // removed from the set of known devices associated with the adapter with
-    // object path |adapter_path|.
-    virtual void DeviceLost(const dbus::ObjectPath& object_path,
-                            const dbus::ObjectPath& adapter_path) {}
+    // removed from the set of known devices.
+    virtual void DeviceLost(const dbus::ObjectPath& object_path) {}
 
     // Called when the device property with the name |property_name| on device
     // with object path |object_path| has acquired a new value.
diff --git a/chromeos/dbus/nfc_tag_client.cc b/chromeos/dbus/nfc_tag_client.cc
index 37f3c0a..0f44791 100644
--- a/chromeos/dbus/nfc_tag_client.cc
+++ b/chromeos/dbus/nfc_tag_client.cc
@@ -9,7 +9,6 @@
 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
-#include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "chromeos/dbus/fake_nfc_tag_client.h"
 #include "chromeos/dbus/nfc_adapter_client.h"
@@ -21,12 +20,6 @@ using chromeos::nfc_client_helpers::DBusObjectMap;
 
 namespace chromeos {
 
-namespace {
-
-typedef std::vector<dbus::ObjectPath> ObjectPathVector;
-
-}  // namespace
-
 NfcTagClient::Properties::Properties(
     dbus::ObjectProxy* object_proxy,
     const PropertyChangedCallback& callback)
@@ -153,41 +146,10 @@ class NfcTagClientImpl : public NfcTagClient,
 
     VLOG(1) << "NFC tags changed.";
 
-    // Add all the new tags.
-    const ObjectPathVector& received_tags =
+    // Update the known tags.
+    const std::vector<dbus::ObjectPath>& received_tags =
         adapter_properties->tags.value();
-    for (ObjectPathVector::const_iterator iter = received_tags.begin();
-         iter != received_tags.end(); ++iter) {
-      const dbus::ObjectPath &tag_path = *iter;
-      if (object_map_->AddObject(tag_path)) {
-        VLOG(1) << "Found NFC tag: " << tag_path.value();
-        FOR_EACH_OBSERVER(NfcTagClient::Observer, observers_,
-                          TagFound(tag_path, object_path));
-      }
-    }
-
-    // Remove all tags that were lost.
-    const DBusObjectMap::ObjectMap& known_tags =
-        object_map_->object_map();
-    std::set<dbus::ObjectPath> tags_set(received_tags.begin(),
-                                        received_tags.end());
-    DBusObjectMap::ObjectMap::const_iterator iter = known_tags.begin();
-    while (iter != known_tags.end()) {
-      // Make a copy here, as the iterator will be invalidated by
-      // DBusObjectMap::RemoveObject below, but |device_path| is needed to
-      // notify observers right after. We want to make sure that we notify
-      // the observers AFTER we remove the object, so that method calls
-      // to the removed object paths in observer implementations fail
-      // gracefully.
-      dbus::ObjectPath tag_path = iter->first;
-      ++iter;
-      if (!ContainsKey(tags_set, tag_path)) {
-        VLOG(1) << "Lost NFC tag: " << tag_path.value();
-        object_map_->RemoveObject(tag_path);
-        FOR_EACH_OBSERVER(NfcTagClient::Observer, observers_,
-                          TagLost(tag_path, object_path));
-      }
-    }
+    object_map_->UpdateObjects(received_tags);
   }
 
   // nfc_client_helpers::DBusObjectMap::Delegate override.
@@ -200,6 +162,17 @@ class NfcTagClientImpl : public NfcTagClient,
                    object_proxy->object_path()));
   }
 
+  // nfc_client_helpers::DBusObjectMap::Delegate override.
+  virtual void ObjectAdded(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcTagClient::Observer, observers_,
+                      TagFound(object_path));
+  }
+
+  virtual void ObjectRemoved(const dbus::ObjectPath& object_path) OVERRIDE {
+    FOR_EACH_OBSERVER(NfcTagClient::Observer, observers_,
+                      TagLost(object_path));
+  }
+
   // Called by NfcPropertySet when a property value is changed, either by
   // result of a signal or response to a GetAll() or Get() call.
   void OnPropertyChanged(const dbus::ObjectPath& object_path,
diff --git a/chromeos/dbus/nfc_tag_client.h b/chromeos/dbus/nfc_tag_client.h
index 5d7e1e0..a719e5a 100644
--- a/chromeos/dbus/nfc_tag_client.h
+++ b/chromeos/dbus/nfc_tag_client.h
@@ -53,16 +53,12 @@ class CHROMEOS_EXPORT NfcTagClient : public DBusClient {
     virtual ~Observer() {}
 
     // Called when a remote NFC tag with the object path |object_path| is added
-    // to the set of known tags associated with the adapter with object path
-    // |adapter_path|.
-    virtual void TagFound(const dbus::ObjectPath& object_path,
-                          const dbus::ObjectPath& adapter_path) {}
+    // to the set of known tags.
+    virtual void TagFound(const dbus::ObjectPath& object_path) {}
 
     // Called when a remote NFC tag with the object path |object_path| is
-    // removed from the set of known tags associated with the adapter with the
-    // object path |adapter_path|.
-    virtual void TagLost(const dbus::ObjectPath& object_path,
-                         const dbus::ObjectPath& adapter_path) {}
+    // removed from the set of known tags.
+    virtual void TagLost(const dbus::ObjectPath& object_path) {}
 
     // Called when the tag property with the name |property_name| on tag with
     // object path |object_path| has acquired a new value.