Added Aura notification that relaunch and powerwash is required in case of downgrade.

chrome/browser/chromeos/upgrade_detector_chromeos.cc

Index: chrome/browser/chromeos/upgrade_detector_chromeos.cc
diff --git a/chrome/browser/chromeos/upgrade_detector_chromeos.cc b/chrome/browser/chromeos/upgrade_detector_chromeos.cc
index 7b22f9214053679f6c8176cec8a5f8b2da59ce6e..a96bf8d9874aec6b77006ffb6fb0fb15ac6ba4b3 100644
--- a/chrome/browser/chromeos/upgrade_detector_chromeos.cc
+++ b/chrome/browser/chromeos/upgrade_detector_chromeos.cc
@@ -7,18 +7,74 @@
 #include "base/memory/singleton.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 
+using chromeos::DBusThreadManager;
+using chromeos::UpdateEngineClient;
+
 namespace {
 
 // How long to wait (each cycle) before checking which severity level we should
 // be at. Once we reach the highest severity, the timer will stop.
 const int kNotifyCycleTimeMs = 20 * 60 * 1000;  // 20 minutes.
 
+bool IsTargetChannelMoreStable(const std::string& current_channel,
+                               const std::string& target_channel) {

[stevenjb, 2014/10/01 22:26:44]

This should either be moved to UpdateEngineClient (where hopefully
:kReleaseChannelsList is reasonably well documented), or should be documented
here, it's not obvious why this works.
 

[ygorshenin1, 2014/10/02 14:21:35]

Done.

+  const auto& channels_list = UpdateEngineClient::kReleaseChannelsList;
+  auto cix =
+      std::find(channels_list.cbegin(), channels_list.cend(), current_channel);
+  auto tix =
+      std::find(channels_list.cbegin(), channels_list.cend(), target_channel);
+  return tix > cix;
+}
+
 }  // namespace
 
-using chromeos::DBusThreadManager;
-using chromeos::UpdateEngineClient;
+class UpgradeDetectorChromeos::ChannelsRequester {
+ public:
+  ChannelsRequester() : weak_factory_(this) {}
+
+  void RequestChannels(const base::Callback<
+      void(const std::string&, const std::string&)>& callback) {

[stevenjb, 2014/10/01 22:26:44]

This callback should be typedfed somewhere

[ygorshenin1, 2014/10/02 14:21:35]

Done.

+    UpdateEngineClient* client =
+        DBusThreadManager::Get()->GetUpdateEngineClient();
+    callback_ = callback;
+    client->GetChannel(true /* get_current_channel */,
+                       base::Bind(&ChannelsRequester::SetCurrentChannel,
+                                  weak_factory_.GetWeakPtr()));
+    client->GetChannel(false /* get_current_channel */,
+                       base::Bind(&ChannelsRequester::SetTargetChannel,
+                                  weak_factory_.GetWeakPtr()));
+  }
+
+ private:
+  void SetCurrentChannel(const std::string& current_channel) {

[stevenjb, 2014/10/01 22:26:44]

DCHECK(!current_channel.empty()), otherwise an empty result will cause
TriggerCallbackIfReady to never fire.

[ygorshenin1, 2014/10/02 14:21:35]

Done.

+    current_channel_ = current_channel;
+    TriggerCallbackIfReady();
+  }
+
+  void SetTargetChannel(const std::string& target_channel) {

[stevenjb, 2014/10/01 22:26:44]

Ditto.

[ygorshenin1, 2014/10/02 14:21:35]

Done.

+    target_channel_ = target_channel;
+    TriggerCallbackIfReady();
+  }
+
+  void TriggerCallbackIfReady() {
+    if (current_channel_.empty() || target_channel_.empty())
+      return;
+    if (!callback_.is_null())
+      callback_.Run(current_channel_, target_channel_);
+  }
+
+  std::string current_channel_;
+  std::string target_channel_;
+
+  base::Callback<void(const std::string&, const std::string&)> callback_;
 
-UpgradeDetectorChromeos::UpgradeDetectorChromeos() : initialized_(false) {
+  base::WeakPtrFactory<ChannelsRequester> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChannelsRequester);
+};
+
+UpgradeDetectorChromeos::UpgradeDetectorChromeos()
+    : initialized_(false), weak_factory_(this) {
 }
 
 UpgradeDetectorChromeos::~UpgradeDetectorChromeos() {
@@ -43,13 +99,10 @@ void UpgradeDetectorChromeos::UpdateStatusChanged(
 
   upgrade_detected_time_ = base::Time::Now();
 
-  // ChromeOS shows upgrade arrow once the upgrade becomes available.
-  NotifyOnUpgrade();
-
-  // Setup timer to to move along the upgrade advisory system.
-  upgrade_notification_timer_.Start(
-      FROM_HERE, base::TimeDelta::FromMilliseconds(kNotifyCycleTimeMs),
-      this, &UpgradeDetectorChromeos::NotifyOnUpgrade);
+  channels_requester_.reset(new UpgradeDetectorChromeos::ChannelsRequester());
+  channels_requester_->RequestChannels(
+      base::Bind(&UpgradeDetectorChromeos::OnChannelsReceived,
+                 weak_factory_.GetWeakPtr()));
 }
 
 void UpgradeDetectorChromeos::NotifyOnUpgrade() {
@@ -80,6 +133,23 @@ void UpgradeDetectorChromeos::NotifyOnUpgrade() {
   NotifyUpgradeRecommended();
 }
 
+void UpgradeDetectorChromeos::OnChannelsReceived(
+    const std::string& current_channel,
+    const std::string& target_channel) {
+  set_is_factory_reset_required(
+      IsTargetChannelMoreStable(current_channel, target_channel));

[stevenjb, 2014/10/01 22:26:44]

Could you add a comment explaining why IsTargetChannelMoreStable corresponds to
factory_reset_required?

[ygorshenin1, 2014/10/02 14:21:35]

Done.

+
+  // ChromeOS shows upgrade arrow once the upgrade becomes available.
+  NotifyOnUpgrade();
+
+  // Setup timer to to move along the upgrade advisory system.
+  upgrade_notification_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kNotifyCycleTimeMs),
+      this,
+      &UpgradeDetectorChromeos::NotifyOnUpgrade);
+}
+
 // static
 UpgradeDetectorChromeos* UpgradeDetectorChromeos::GetInstance() {
   return Singleton<UpgradeDetectorChromeos>::get();