VmCameraMicManager: Implement a debounce algorithm for notifications

There is a long description about why we need this and how the algorithm
work just above class VmInfo in vm_camera_mic_manager.cc.

Bug: b/167491603
Change-Id: I7894609dd7d19ae1e69097508e942fca5792cfa8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643417
Commit-Queue: Jason Lin <lxj@google.com>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846058}

chrome/browser/chromeos/camera_mic/vm_camera_mic_manager.cc

@@ -16,6 +16,7 @@
 #include "base/strings/string16.h"
 #include "base/system/sys_info.h"
 #include "base/time/time.h"
+#include "base/timer/timer.h"
 #include "chrome/app/vector_icons/vector_icons.h"
 #include "chrome/browser/chromeos/plugin_vm/plugin_vm_util.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
@@ -41,8 +42,6 @@ namespace chromeos {
 namespace {
 
 const char kNotificationIdPrefix[] = "vm_camera_mic_manager";
-const base::TimeDelta kObserverTimerDelay =
-    base::TimeDelta::FromMilliseconds(100);
 
 }  // namespace
 
@@ -54,22 +53,103 @@ constexpr VmCameraMicManager::NotificationType
     VmCameraMicManager::kCameraNotification;
 constexpr VmCameraMicManager::NotificationType
     VmCameraMicManager::kCameraAndMicNotification;
-
+constexpr base::TimeDelta VmCameraMicManager::kDebounceTime;
+
+// VmInfo stores the camera/mic information for a VM. It also controls the
+// notifications for the VM. We either do not display a notification at all, or
+// display a single notification, which can be a "camera", "mic", or a "camera
+// and mic" notification.
+//
+// Some apps will quickly turn on and off devices multiple times (e.g. skype in
+// Parallels does this about 5 times when starting a meeting). To avoid flashing
+// multiple notifications, we implement a debounce algorithm here. The debounce
+// algorithm needs to handle the following situations:
+//
+// * when a VM opens the camera and mic subsequently with a small delay
+//   in-between, we should only show the "camera and mic" notification, instead
+//   of showing the "camera" notification first and then switching to the
+//   "camera and mic" one.
+// * when a VM turns on a device and then immediately turns it off (e.g. taking
+//   a photo), we should make sure the notification is shown (for a short period
+//   of time). So, the debounce algorithm should not naively accumulate device
+//   changes and then only act on the final accumulated state.
+//
+//
+// How the debounce algorithm works
+// ================================
+//
+// Basically, when a new device update comes, the algorithm starts a debounce
+// period for `kDebounceTime`, during which we record the changes, and we update
+// the notification one or more times afterwards.
+//
+// The type of notification is represented by `NotificationType`, which is a
+// bitset of two bits. For a "camera" notification, only the camera bit is set
+// (i.e. `10`). A "camera and mic" notification sets both bits (i.e. `11`). If
+// no notification should be shown, we set both bits to 0 (i.e. `00`).
+//
+// Our algorithm maintains 3 `NotificationType` variables (see
+// `notifications_`):
+//
+// * active: this is what is currently displaying. When we say setting `active`
+//           to some value, we also mean updating the displaying notification.
+// * target: this is updated immediately whenever device updates come in, so it
+//           represents the latest state. If a device is turned on and off
+//           immediately, obviously the effect is erased from target. This is
+//           why we need another variable `stage`.
+// * stage: this is updated immediately whenever a device is turned *on*.
+//          Turning off a device does not affect this directly.
+//
+// This algorithm for updating `target` and `stage` is implemented in
+// `OnDeviceUpdated()`, which also starts/stops the debounce timer if necessary.
+//
+// When `active == stage == target`, we are "stable" --- we don't need to do
+// anything (until the next device update). And `SyncNotification()` is normally
+// what brings us to stable. It is called when the timer expired. This is what
+// it does:
+//
+// * If `active != stage`, we set `active = stage`. Timer is reset if we are
+//   still not stable.
+// * Otherwise, `active == stage != target`. we set `active = stage = target`.
+//   We reach the stable state now.
+//
+// Here is an example where the mic is turned on, the camera is turned on and
+// then off immediately, and mic is turned off at the end after some time. We
+// denote the state of the system with 6 bits: <active>-<stage>-<target>.
+//
+// 1: 00-00-00  # Stable, nothing is on.
+// 2: 00-01-01  # Mic turning on, debounce timer is started.
+// 3: 00-11-11  # Camera turning on, still in debounce period.
+// 4: 00-11-01  # Camera turning off, still in debounce period.
+// 5: 11-11-01  # Timer expired. `SyncNotification()` sets `active=stage` (shows
+//              # "camera and mic" notification). Reset the timer.
+// 6: 01-01-01  # Timer expired. `SyncNotification()` sets `active=stage=target`
+//              # (shows mic notification).  We are stable now.
+// 7: 01-01-00  # Mic turning off, debounce timer is started.
+// 8: 00-00-00  # Timer expired. Same as 6, but no notification is shown now.
+//              # Reach stable again.
 class VmCameraMicManager::VmInfo : public message_center::NotificationObserver {
  public:
-  VmInfo(Profile* profile, VmType vm_type, int name_id)
-      : profile_(profile), vm_type_(vm_type), name_id_(name_id) {}
+  VmInfo(Profile* profile,
+         VmType vm_type,
+         int name_id,
+         base::RepeatingClosure on_notification_changed)
+      : profile_(profile),
+        vm_type_(vm_type),
+        name_id_(name_id),
+        notification_changed_callback_(on_notification_changed),
+        debounce_timer_(FROM_HERE,
+                        kDebounceTime,
+                        base::BindRepeating(&VmInfo::SyncNotification,
+                                            // Unretained because the timer
+                                            // cannot outlive the parent.
+                                            base::Unretained(this))) {}
   ~VmInfo() = default;
 
   VmType vm_type() const { return vm_type_; }
   int name_id() const { return name_id_; }
-  NotificationType notification_type() const { return notification_type_; }
+  NotificationType notification_type() const { return notifications_.active; }
 
-  void SetMicActive(bool active) {
-    target_notification_type_.set(static_cast<size_t>(DeviceType::kMic),
-                                  active);
-    UpdateNotification();
-  }
+  void SetMicActive(bool active) { OnDeviceUpdated(DeviceType::kMic, active); }
 
   void SetCameraAccessing(bool accessing) {
     camera_accessing_ = accessing;
@@ -82,26 +162,73 @@ class VmCameraMicManager::VmInfo : public message_center::NotificationObserver {
 
  private:
   void OnCameraUpdated() {
-    target_notification_type_.set(static_cast<size_t>(DeviceType::kCamera),
+    OnDeviceUpdated(DeviceType::kCamera,
                     camera_accessing_ && !camera_privacy_is_on_);
-    UpdateNotification();
   }
 
-  void UpdateNotification() {
-    if (notification_type_ == target_notification_type_) {
-      return;
+  // See document at the beginning of class.
+  void OnDeviceUpdated(DeviceType device, bool value) {
+    size_t device_index = static_cast<size_t>(device);
+
+    notifications_.target.set(device_index, value);
+    if (value) {
+      notifications_.stage.set(device_index, value);
     }
 
-    // We always show 0 or 1 notifications for a VM, so here we just need to
-    // close the previous one if it exists and open the new one if necessary.
-    if (notification_type_ != kNoNotification) {
-      CloseNotification(notification_type_);
+    VLOG(1) << "update stage/target vm_type=" << static_cast<int>(vm_type_)
+            << " state: " << notifications_.active << "-"
+            << notifications_.stage << "-" << notifications_.target;
+
+    SyncTimer();
+  }
+
+  void SyncTimer() {
+    const bool stable = notifications_.active == notifications_.stage &&
+                        notifications_.active == notifications_.target;
+    const bool should_run_timer = !stable;
+    const bool is_running = debounce_timer_.IsRunning();
+
+    if (should_run_timer && !is_running) {
+      debounce_timer_.Reset();
+    } else if (!should_run_timer && is_running) {
+      debounce_timer_.Stop();
     }
-    if (target_notification_type_ != kNoNotification) {
-      OpenNotification(target_notification_type_);
   }
 
-    notification_type_ = target_notification_type_;
+  void UpdateActiveNotification(NotificationType new_notification) {
+    DCHECK_NE(notifications_.active, new_notification);
+
+    if (notifications_.active != kNoNotification) {
+      CloseNotification(notifications_.active);
+    }
+    if (new_notification != kNoNotification) {
+      OpenNotification(new_notification);
+    }
+    notifications_.active = new_notification;
+    notification_changed_callback_.Run();
+  }
+
+  // See document at the beginning of class.
+  void SyncNotification() {
+    if (notifications_.active != notifications_.stage) {
+      UpdateActiveNotification(notifications_.stage);
+      SyncTimer();
+
+      VLOG(1) << "sync from stage. vm_type=" << static_cast<int>(vm_type_)
+              << " state: " << notifications_.active << "-"
+              << notifications_.stage << "-" << notifications_.target;
+      return;
+    }
+
+    // Only target notification is different.
+    DCHECK_NE(notifications_.active, notifications_.target);
+    notifications_.stage = notifications_.target;
+    UpdateActiveNotification(notifications_.target);
+    VLOG(1) << "sync from target. vm_type=" << static_cast<int>(vm_type_)
+            << " state: " << notifications_.active << "-"
+            << notifications_.stage << "-" << notifications_.target;
+    // No need to call `SyncTimer()` because we have reached the stable state
+    // here.
   }
 
   void OpenNotification(NotificationType type) const {
@@ -189,14 +316,21 @@ class VmCameraMicManager::VmInfo : public message_center::NotificationObserver {
   Profile* const profile_;
   const VmType vm_type_;
   const int name_id_;
+  base::RepeatingClosure notification_changed_callback_;
 
   bool camera_accessing_ = false;
   // We don't actually need to store this separately for each VM, but this
   // makes code simpler.
   bool camera_privacy_is_on_ = false;
 
-  NotificationType notification_type_;
-  NotificationType target_notification_type_;
+  // See document at the beginning of class.
+  struct {
+    NotificationType active;
+    NotificationType stage;
+    NotificationType target;
+  } notifications_;
+
+  base::RetainingOneShotTimer debounce_timer_;
 
   base::WeakPtrFactory<VmInfo> weak_ptr_factory_{this};
 };
@@ -206,14 +340,7 @@ VmCameraMicManager* VmCameraMicManager::Get() {
   return manager.get();
 }
 
-VmCameraMicManager::VmCameraMicManager()
-    : observer_timer_(
-          FROM_HERE,
-          kObserverTimerDelay,
-          base::BindRepeating(&VmCameraMicManager::NotifyActiveChanged,
-                              // Unretained because the timer cannot
-                              // live longer than the manager.
-                              base::Unretained(this))) {}
+VmCameraMicManager::VmCameraMicManager() = default;
 
 void VmCameraMicManager::OnPrimaryUserSessionStarted(Profile* primary_profile) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
@@ -221,8 +348,12 @@ void VmCameraMicManager::OnPrimaryUserSessionStarted(Profile* primary_profile) {
   primary_profile_ = primary_profile;
 
   auto emplace_vm_info = [this](VmType vm, int name_id) {
-    vm_info_map_.emplace(std::piecewise_construct, std::forward_as_tuple(vm),
-                         std::forward_as_tuple(primary_profile_, vm, name_id));
+    vm_info_map_.emplace(
+        std::piecewise_construct, std::forward_as_tuple(vm),
+        std::forward_as_tuple(
+            primary_profile_, vm, name_id,
+            base::BindRepeating(&VmCameraMicManager::NotifyActiveChanged,
+                                base::Unretained(this))));
   };
 
   emplace_vm_info(VmType::kCrostiniVm, IDS_CROSTINI_LINUX);
@@ -274,10 +405,6 @@ void VmCameraMicManager::UpdateVmInfo(VmType vm,
   auto& vm_info = it->second;
 
   (vm_info.*updator)(value);
-
-  if (!observer_timer_.IsRunning()) {
-    observer_timer_.Reset();
-  }
 }
 
 bool VmCameraMicManager::IsDeviceActive(DeviceType device) const {

chrome/browser/chromeos/camera_mic/vm_camera_mic_manager.h

@@ -14,7 +14,6 @@
 #include "base/observer_list.h"
 #include "base/observer_list_types.h"
 #include "base/scoped_observation.h"
-#include "base/timer/timer.h"
 #include "chromeos/audio/cras_audio_handler.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "media/capture/video/chromeos/camera_hal_dispatcher_impl.h"
@@ -53,6 +52,9 @@ class VmCameraMicManager : public media::CameraActiveClientObserver,
       (1 << static_cast<size_t>(DeviceType::kMic)) |
       (1 << static_cast<size_t>(DeviceType::kCamera))};
 
+  static constexpr base::TimeDelta kDebounceTime =
+      base::TimeDelta::FromMilliseconds(300);
+
   class Observer : public base::CheckedObserver {
    public:
     virtual void OnVmCameraMicActiveChanged(VmCameraMicManager*) {}
@@ -109,7 +111,6 @@ class VmCameraMicManager : public media::CameraActiveClientObserver,
   Profile* primary_profile_ = nullptr;
   std::map<VmType, VmInfo> vm_info_map_;
 
-  base::RetainingOneShotTimer observer_timer_;
   base::ObserverList<Observer> observers_;
 };
 

chrome/browser/chromeos/camera_mic/vm_camera_mic_manager_unittest.cc

@@ -12,6 +12,7 @@
 #include "base/bind.h"
 #include "base/containers/flat_map.h"
 #include "base/test/scoped_feature_list.h"
+#include "base/time/time.h"
 #include "chrome/browser/chromeos/login/users/mock_user_manager.h"
 #include "chrome/browser/notifications/notification_display_service.h"
 #include "chrome/browser/notifications/notification_display_service_factory.h"
@@ -42,6 +43,8 @@ constexpr NotificationType kCameraNotification =
 constexpr NotificationType kCameraAndMicNotification =
     chromeos::VmCameraMicManager::kCameraAndMicNotification;
 
+constexpr auto kDebounceTime = chromeos::VmCameraMicManager::kDebounceTime;
+
 class FakeNotificationDisplayService : public NotificationDisplayService {
  public:
   FakeNotificationDisplayService() = default;
@@ -112,6 +115,10 @@ class VmCameraMicManagerTest : public testing::Test {
     }
   };
 
+  std::string GetNotificationId(VmType vm, NotificationType type) {
+    return VmCameraMicManager::GetNotificationId(vm, type);
+  }
+
   VmCameraMicManagerTest() {
     // Make the profile the primary one.
     auto mock_user_manager =
@@ -150,7 +157,7 @@ class VmCameraMicManagerTest : public testing::Test {
   }
 
   // Note that camera privacy is always set to off by this function.
-  void SetActive(const ActiveMap& active_map) {
+  void SetActiveAndForwardToStable(const ActiveMap& active_map) {
     SetCameraPrivacyIsOn(false);
     for (const auto& vm_and_device_active_map : active_map) {
       VmType vm = vm_and_device_active_map.first;
@@ -165,10 +172,21 @@ class VmCameraMicManagerTest : public testing::Test {
         }
       }
     }
+
+    ForwardToStable();
+  }
+
+  void ForwardToStable() {
+    // The manager at most does the debounce twice (once for "stage" and once
+    // for "target"), so waiting 2 times here is enough.
+    for (size_t i = 0; i < 2; ++i) {
+      task_environment_.FastForwardBy(kDebounceTime);
+    }
   }
 
  protected:
-  content::BrowserTaskEnvironment task_environment_;
+  content::BrowserTaskEnvironment task_environment_{
+      base::test::TaskEnvironment::TimeSource::MOCK_TIME};
   TestingProfile testing_profile_;
   std::unique_ptr<user_manager::ScopedUserManager> scoped_user_manager_;
   base::test::ScopedFeatureList scoped_feature_list_;
@@ -182,24 +200,28 @@ class VmCameraMicManagerTest : public testing::Test {
 TEST_F(VmCameraMicManagerTest, CameraPrivacy) {
   SetCameraAccessing(kPluginVm, false);
   SetCameraPrivacyIsOn(false);
+  ForwardToStable();
   EXPECT_FALSE(vm_camera_mic_manager_->IsDeviceActive(kCamera));
   EXPECT_FALSE(
       vm_camera_mic_manager_->IsNotificationActive(kCameraNotification));
 
   SetCameraAccessing(kPluginVm, true);
   SetCameraPrivacyIsOn(false);
+  ForwardToStable();
   EXPECT_TRUE(vm_camera_mic_manager_->IsDeviceActive(kCamera));
   EXPECT_TRUE(
       vm_camera_mic_manager_->IsNotificationActive(kCameraNotification));
 
   SetCameraAccessing(kPluginVm, false);
   SetCameraPrivacyIsOn(true);
+  ForwardToStable();
   EXPECT_FALSE(vm_camera_mic_manager_->IsDeviceActive(kCamera));
   EXPECT_FALSE(
       vm_camera_mic_manager_->IsNotificationActive(kCameraNotification));
 
   SetCameraAccessing(kPluginVm, true);
   SetCameraPrivacyIsOn(true);
+  ForwardToStable();
   EXPECT_FALSE(vm_camera_mic_manager_->IsDeviceActive(kCamera));
   EXPECT_FALSE(
       vm_camera_mic_manager_->IsNotificationActive(kCameraNotification));
@@ -211,7 +233,7 @@ class VmCameraMicManagerIsActiveTest
       public testing::WithParamInterface<IsActiveTestParam> {};
 
 TEST_P(VmCameraMicManagerIsActiveTest, IsNotificationActive) {
-  SetActive(GetParam().active_map);
+  SetActiveAndForwardToStable(GetParam().active_map);
 
   for (auto device : {kCamera, kMic}) {
     EXPECT_EQ(vm_camera_mic_manager_->IsDeviceActive(device),
@@ -360,9 +382,9 @@ class VmCameraMicManagerNotificationTest
   }
 };
 
-TEST_P(VmCameraMicManagerNotificationTest, SetActive) {
+TEST_P(VmCameraMicManagerNotificationTest, SetActiveAndForwardToStable) {
   const NotificationTestParam& param = GetParam();
-  SetActive(param.active_map);
+  SetActiveAndForwardToStable(param.active_map);
   EXPECT_EQ(fake_display_service_->notification_ids(),
             param.expected_notifications);
 }
@@ -372,4 +394,140 @@ INSTANTIATE_TEST_SUITE_P(
     VmCameraMicManagerNotificationTest,
     testing::ValuesIn(VmCameraMicManagerNotificationTest::GetTestValues()));
 
+// For testing the debounce behavior.
+class VmCameraMicManagerDebounceTest : public VmCameraMicManagerTest {
+ public:
+  void ForwardDebounceTime(double factor = 1) {
+    task_environment_.FastForwardBy(factor * kDebounceTime);
+  }
+};
+
+TEST_F(VmCameraMicManagerDebounceTest, Simple) {
+  SetMicActive(kPluginVm, true);
+  ForwardDebounceTime();
+  EXPECT_EQ(
+      fake_display_service_->notification_ids(),
+      std::set<std::string>{GetNotificationId(kPluginVm, kMicNotification)});
+
+  ForwardToStable();
+  EXPECT_EQ(
+      fake_display_service_->notification_ids(),
+      std::set<std::string>{GetNotificationId(kPluginVm, kMicNotification)});
+}
+
+TEST_F(VmCameraMicManagerDebounceTest, CombineCameraAndMic) {
+  SetMicActive(kPluginVm, true);
+  ForwardDebounceTime(/*factor=*/0.51);
+  // Within debounce time, so no notification.
+  EXPECT_EQ(fake_display_service_->notification_ids(), std::set<std::string>{});
+
+  SetCameraAccessing(kPluginVm, true);
+  ForwardDebounceTime(/*factor=*/0.51);
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+}
+
+// This test that if the devices are turned on and then immediately turned off,
+// we will still show notifications for at least kDebounceTime.
+TEST_F(VmCameraMicManagerDebounceTest, DisplayStageBeforeTarget) {
+  SetMicActive(kPluginVm, true);
+  SetMicActive(kPluginVm, false);
+  SetCameraAccessing(kPluginVm, true);
+  SetCameraAccessing(kPluginVm, false);
+
+  ForwardDebounceTime();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  // Will continue displaying for roughly kDebounceTime.
+  ForwardDebounceTime(/*factor=*/0.9);
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  // Eventually display the "target" notification, which is no notification at
+  // all.
+  ForwardDebounceTime(/*factor=*/0.11);
+  EXPECT_EQ(fake_display_service_->notification_ids(), std::set<std::string>{});
+
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(), std::set<std::string>{});
+}
+
+// This test that within debounce time, if the state is reverted back to the
+// stable status, then nothing will change.
+TEST_F(VmCameraMicManagerDebounceTest, RevertBackToStable) {
+  SetMicActive(kPluginVm, true);
+  SetCameraAccessing(kPluginVm, true);
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  // First turn both devices off, and then turn them back up. The state should
+  // become stable again so nothing should changed.
+  SetMicActive(kPluginVm, false);
+  SetCameraAccessing(kPluginVm, false);
+  ForwardDebounceTime(/*factor=*/0.5);
+  SetMicActive(kPluginVm, true);
+  SetCameraAccessing(kPluginVm, true);
+
+  // Nothing changed.
+  ForwardDebounceTime();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+}
+
+// Simulate one of the more complicated case.
+TEST_F(VmCameraMicManagerDebounceTest, SimulateSkypeStartingMeeting) {
+  // Simulate the waiting to start screen, in which only the camera is active.
+  SetCameraAccessing(kPluginVm, true);
+  ForwardToStable();
+  EXPECT_EQ(
+      fake_display_service_->notification_ids(),
+      std::set<std::string>{GetNotificationId(kPluginVm, kCameraNotification)});
+
+  // Simulate what happens after clicking the starting button. Skype will turn
+  // on and off the devices multiple time. We should expect the notification
+  // only changes to "camera and mic" once.
+  SetCameraAccessing(kPluginVm, false);
+  ForwardDebounceTime(0.2);
+  SetMicActive(kPluginVm, true);
+  ForwardDebounceTime(0.2);
+  SetCameraAccessing(kPluginVm, true);
+  ForwardDebounceTime(0.7);
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+
+  SetCameraAccessing(kPluginVm, false);
+  ForwardDebounceTime(0.2);
+  SetCameraAccessing(kPluginVm, true);
+  ForwardDebounceTime(0.9);
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+  ForwardToStable();
+  EXPECT_EQ(fake_display_service_->notification_ids(),
+            std::set<std::string>{
+                GetNotificationId(kPluginVm, kCameraAndMicNotification)});
+}
+
 }  // namespace chromeos