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

chromeos/dbus/update_engine_client.cc

 // Copyright (c) 2012 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 "chromeos/dbus/update_engine_client.h"
 
+#include <algorithm>
+
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
+#include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
 #include "chromeos/chromeos_switches.h"
 #include "dbus/bus.h"
 #include "dbus/message.h"
 #include "dbus/object_path.h"
 #include "dbus/object_proxy.h"
 #include "third_party/cros_system_api/dbus/service_constants.h"
 
 namespace chromeos {
 
 namespace {
 
 const char kReleaseChannelDev[] = "dev-channel";
 const char kReleaseChannelBeta[] = "beta-channel";
 const char kReleaseChannelStable[] = "stable-channel";
 
+// List of release channels ordered by stability.
+const char* kReleaseChannelsList[] = {kReleaseChannelDev,
+                                      kReleaseChannelBeta,
+                                      kReleaseChannelStable};
+
 // Delay between successive state transitions during AU.
 const int kStateTransitionDefaultDelayMs = 3000;
 
 // Delay between successive notifications about downloading progress
 // during fake AU.
 const int kStateTransitionDownloadingDelayMs = 250;
 
 // Size of parts of a "new" image which are downloaded each
 // |kStateTransitionDownloadingDelayMs| during fake AU.
 const int64_t kDownloadSizeDelta = 1 << 19;
@@ skipping 22 matching lines @@
     return UpdateEngineClient::UPDATE_STATUS_ATTEMPTING_ROLLBACK;
   return UpdateEngineClient::UPDATE_STATUS_ERROR;
 }
 
 // Used in UpdateEngineClient::EmptyUpdateCheckCallback().
 void EmptyUpdateCheckCallbackBody(
     UpdateEngineClient::UpdateCheckResult unused_result) {
 }
 
 bool IsValidChannel(const std::string& channel) {
-  return channel == kReleaseChannelDev ||
-      channel == kReleaseChannelBeta ||
-      channel == kReleaseChannelStable;
+  return channel == kReleaseChannelDev || channel == kReleaseChannelBeta ||
+         channel == kReleaseChannelStable;
 }
 
 }  // namespace
 
 // The UpdateEngineClient implementation used in production.
 class UpdateEngineClientImpl : public UpdateEngineClient {
  public:
   UpdateEngineClientImpl()
       : update_engine_proxy_(NULL), last_status_(), weak_ptr_factory_(this) {}
 
@@ skipping 472 matching lines @@
     DBusClientImplementationType type) {
   if (type == REAL_DBUS_CLIENT_IMPLEMENTATION)
     return new UpdateEngineClientImpl();
   DCHECK_EQ(STUB_DBUS_CLIENT_IMPLEMENTATION, type);
   if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTestAutoUpdateUI))
     return new UpdateEngineClientFakeImpl();
   else
     return new UpdateEngineClientStubImpl();
 }
 
+// static
+bool UpdateEngineClient::IsTargetChannelMoreStable(
+    const std::string& current_channel,
+    const std::string& target_channel) {
+  auto cix = std::find(kReleaseChannelsList,
+                       kReleaseChannelsList + arraysize(kReleaseChannelsList),
+                       current_channel);
+  auto tix = std::find(kReleaseChannelsList,
+                       kReleaseChannelsList + arraysize(kReleaseChannelsList),
+                       target_channel);
+  return tix > cix;
+}
+
 }  // namespace chromeos