Create an observer to purge network icons

This cl moves network icon cache purging to a new observer that is owned
by the unified system tray.

Currently there are five subclasses of
TrayNetworkStateObserver::Delegate. Every time we get a network list
update the global network icon cache is purged.
This means that for every update the cache is purged at least five
times.

With this cl TrayNetworkStateObserver::Delegate can still be used as a
simple way of subscribing to all network events without excessive icon
purging.

Bug: 902409
Change-Id: I078ac8dbdee473fc285ee8e91f735c99524c74a7
Reviewed-on: https://chromium-review.googlesource.com/c/1334835
Commit-Queue: Tony De Luna <tonydeluna@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608230}

ash/BUILD.gn

@@ -762,6 +762,8 @@ component("ash") {
     "system/network/network_icon_animation.cc",
     "system/network/network_icon_animation.h",
     "system/network/network_icon_animation_observer.h",
+    "system/network/network_icon_purger.cc",
+    "system/network/network_icon_purger.h",
     "system/network/network_info.cc",
     "system/network/network_info.h",
     "system/network/network_list.cc",

ash/system/network/network_icon_purger.cc

+// Copyright 2018 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 "ash/system/network/network_icon_purger.h"
+
+#include "ash/system/network/network_icon.h"
+#include "base/bind.h"
+#include "chromeos/network/network_state_handler.h"
+
+using chromeos::NetworkHandler;
+
+namespace {
+const int kPurgeDelayMs = 300;
+}  // namespace
+
+namespace ash {
+
+NetworkIconPurger::NetworkIconPurger() {
+  // NetworkHandler may not be initialized in tests.
+  if (NetworkHandler::IsInitialized()) {
+    auto* network_handler = NetworkHandler::Get();
+    network_handler->network_state_handler()->AddObserver(this, FROM_HERE);
+  }
+}
+
+NetworkIconPurger::~NetworkIconPurger() {
+  // NetworkHandler may not be initialized in tests.
+  if (NetworkHandler::IsInitialized()) {
+    auto* network_handler = NetworkHandler::Get();
+    network_handler->network_state_handler()->RemoveObserver(this, FROM_HERE);
+  }
+}
+
+void NetworkIconPurger::NetworkListChanged() {
+  if (timer_.IsRunning())
+    return;
+  timer_.Start(FROM_HERE, base::TimeDelta::FromMilliseconds(kPurgeDelayMs),
+               base::BindOnce(&network_icon::PurgeNetworkIconCache));
+}
+
+}  // namespace ash

ash/system/network/network_icon_purger.h

+// Copyright 2018 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.
+
+#ifndef ASH_SYSTEM_NETWORK_NETWORK_ICON_PURGER_H_
+#define ASH_SYSTEM_NETWORK_NETWORK_ICON_PURGER_H_
+
+#include "base/macros.h"
+#include "base/timer/timer.h"
+#include "chromeos/network/network_state_handler_observer.h"
+
+namespace ash {
+
+// Purges network icon caches when the network list is updated.
+// Introduces a small delay before purging the cache. This prevents
+// us from excessively purging icon caches when receiving updates
+// in quick succession.
+class NetworkIconPurger : public chromeos::NetworkStateHandlerObserver {
+ public:
+  NetworkIconPurger();
+  ~NetworkIconPurger() override;
+
+  // chromeos::NetworkStateHandlerObserver
+  void NetworkListChanged() override;
+
+ private:
+  base::OneShotTimer timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(NetworkIconPurger);
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_NETWORK_NETWORK_ICON_PURGER_H_

ash/system/network/tray_network_state_observer.cc

@@ -7,7 +7,6 @@
 #include <set>
 #include <string>
 
-#include "ash/system/network/network_icon.h"
 #include "base/location.h"
 #include "chromeos/network/network_state.h"
 #include "chromeos/network/network_state_handler.h"
@@ -31,7 +30,6 @@ namespace ash {
 
 TrayNetworkStateObserver::TrayNetworkStateObserver(Delegate* delegate)
     : delegate_(delegate),
-      purge_icons_(false),
       update_frequency_(kUpdateFrequencyMs) {
   if (ui::ScopedAnimationDurationScaleMode::duration_scale_mode() !=
       ui::ScopedAnimationDurationScaleMode::NORMAL_DURATION) {
@@ -58,7 +56,6 @@ TrayNetworkStateObserver::~TrayNetworkStateObserver() {
 }
 
 void TrayNetworkStateObserver::NetworkListChanged() {
-  purge_icons_ = true;
   SignalUpdate(false /* notify_a11y */);
 }
 
@@ -119,10 +116,6 @@ void TrayNetworkStateObserver::SignalUpdate(bool notify_a11y) {
 
 void TrayNetworkStateObserver::SendNetworkStateChanged(bool notify_a11y) {
   delegate_->NetworkStateChanged(notify_a11y);
-  if (purge_icons_) {
-    network_icon::PurgeNetworkIconCache();
-    purge_icons_ = false;
-  }
 }
 
 }  // namespace ash

ash/system/network/tray_network_state_observer.h

@@ -52,9 +52,6 @@ class TrayNetworkStateObserver
   // Unowned Delegate pointer (must outlive this instance).
   Delegate* delegate_;
 
-  // Set to true when we should purge stale icons in the cache.
-  bool purge_icons_;
-
   // Frequency at which to push NetworkStateChanged updates. This avoids
   // unnecessarily frequent UI updates (which can be expensive). We set this
   // to 0 for tests to eliminate timing variance.

ash/system/unified/unified_system_tray.cc

@@ -14,6 +14,7 @@
 #include "ash/system/message_center/message_center_ui_delegate.h"
 #include "ash/system/model/clock_model.h"
 #include "ash/system/model/system_tray_model.h"
+#include "ash/system/network/network_icon_purger.h"
 #include "ash/system/network/network_tray_view.h"
 #include "ash/system/power/tray_power.h"
 #include "ash/system/status_area_widget.h"
@@ -118,6 +119,7 @@ UnifiedSystemTray::UnifiedSystemTray(Shelf* shelf)
       model_(std::make_unique<UnifiedSystemTrayModel>()),
       slider_bubble_controller_(
           std::make_unique<UnifiedSliderBubbleController>(this)),
+      network_icon_purger_(std::make_unique<NetworkIconPurger>()),
       ime_mode_view_(new ImeModeView(shelf)),
       managed_device_view_(new ManagedDeviceView(shelf)),
       notification_counter_item_(new NotificationCounterView(shelf)),

ash/system/unified/unified_system_tray.h

@@ -25,6 +25,7 @@ class QuietModeView;
 class UnifiedSliderBubbleController;
 class UnifiedSystemTrayBubble;
 class UnifiedSystemTrayModel;
+class NetworkIconPurger;
 
 // UnifiedSystemTray is system menu of Chromium OS, which is typically
 // accessible from the button on the right bottom of the screen (Status Area).
@@ -123,6 +124,8 @@ class ASH_EXPORT UnifiedSystemTray : public TrayBackgroundView {
   const std::unique_ptr<UnifiedSliderBubbleController>
       slider_bubble_controller_;
 
+  const std::unique_ptr<NetworkIconPurger> network_icon_purger_;
+
   ImeModeView* const ime_mode_view_;
   ManagedDeviceView* const managed_device_view_;
   NotificationCounterView* const notification_counter_item_;