Avoid flashing of notification counter for bundled notifications.

This is reland of crrev.com/c/1295633 with some fix.

When ARC++ app builds bundled notifications, multiple individual
notifications are sent and then replaced with a single bundled
notification. The indicator icon showed such update as-is, resulting
in flashing. This change limits the frequency to reflect notification
count updates for avoiding such effect.

Bug: 892021
Change-Id: If7dbfdfdc530d3498f271f9b7b15b2d02b6b216d
Reviewed-on: https://chromium-review.googlesource.com/c/1298829Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603001}

ash/system/unified/unified_system_tray.cc

@@ -27,6 +27,8 @@
 #include "ash/system/unified/unified_slider_bubble_controller.h"
 #include "ash/system/unified/unified_system_tray_bubble.h"
 #include "ash/system/unified/unified_system_tray_model.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
 #include "chromeos/network/network_handler.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/display/display.h"
@@ -65,6 +67,9 @@ class UnifiedSystemTray::UiDelegate : public MessageCenterUiDelegate {
   DISALLOW_COPY_AND_ASSIGN(UiDelegate);
 };
 
+const base::TimeDelta UnifiedSystemTray::kNotificationCountUpdateDelay =
+    base::TimeDelta::FromMilliseconds(100);
+
 UnifiedSystemTray::UiDelegate::UiDelegate(UnifiedSystemTray* owner)
     : owner_(owner) {
   ui_controller_ = std::make_unique<MessageCenterUiController>(this);
@@ -327,6 +332,16 @@ void UnifiedSystemTray::HideBubbleInternal() {
 }
 
 void UnifiedSystemTray::UpdateNotificationInternal() {
+  // Limit update frequency in order to avoid flashing when 2 updates are
+  // incoming in a very short period of time. It happens when ARC++ apps
+  // creating bundled notifications.
+  if (!timer_.IsRunning()) {
+    timer_.Start(FROM_HERE, kNotificationCountUpdateDelay, this,
+                 &UnifiedSystemTray::UpdateNotificationAfterDelay);
+  }
+}
+
+void UnifiedSystemTray::UpdateNotificationAfterDelay() {
   notification_counter_item_->Update();
   quiet_mode_view_->Update();
 }

ash/system/unified/unified_system_tray.h

@@ -9,6 +9,8 @@
 
 #include "ash/ash_export.h"
 #include "ash/system/tray/tray_background_view.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
 
 namespace ash {
 
@@ -97,6 +99,8 @@ class ASH_EXPORT UnifiedSystemTray : public TrayBackgroundView {
   UnifiedSystemTrayModel* model() { return model_.get(); }
 
  private:
+  const static base::TimeDelta kNotificationCountUpdateDelay;
+
   friend class UnifiedSystemTrayTest;
   friend class UnifiedSystemTrayTestApi;
 
@@ -110,6 +114,7 @@ class ASH_EXPORT UnifiedSystemTray : public TrayBackgroundView {
   void ShowBubbleInternal(bool show_by_click);
   void HideBubbleInternal();
   void UpdateNotificationInternal();
+  void UpdateNotificationAfterDelay();
 
   const std::unique_ptr<UiDelegate> ui_delegate_;
 
@@ -130,6 +135,7 @@ class ASH_EXPORT UnifiedSystemTray : public TrayBackgroundView {
   tray::TimeTrayItemView* const time_view_;
 
   ui::Layer* ink_drop_layer_ = nullptr;
+  base::OneShotTimer timer_;
 
   DISALLOW_COPY_AND_ASSIGN(UnifiedSystemTray);
 };