Display "Restart to update" dialog to Chrome OS users.

chrome/browser/ui/ash/system_tray_client.cc

 // Copyright 2016 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 "chrome/browser/ui/ash/system_tray_client.h"
 
 #include "ash/common/login_status.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/wm_shell.h"
 #include "ash/public/cpp/shell_window_ids.h"
@@ skipping 297 matching lines @@
   // User is not logged in.
   CHECK(!login_state->IsUserLoggedIn() ||
         login_state->GetLoggedInUserType() == LoginState::LOGGED_IN_USER_NONE);
   chromeos::LoginDisplayHost::default_host()->OpenProxySettings();
 }
 
 void SystemTrayClient::SignOut() {
   chrome::AttemptUserExit();
 }
 
-void SystemTrayClient::RequestRestartForUpdate() {
+void SystemTrayClient::RequestRestartForUpdate(bool always_reboot) {
   // We expect that UpdateEngine is in "Reboot for update" state now.
-  chrome::NotifyAndTerminate(true /* fast_path */);
+  chrome::NotifyAndTerminate(true /* fast_path */, always_reboot);

[James Cook, 2016/11/30 23:01:41]

For example, this could query
SystemTrayDelegateChromeOS::Get()->GetFlashUpdateAvailable(). (If you do that,
be sure to check that SystemTrayDelegateChromeOS::Get() is not null, for my
project there's a case where SystemTrayClient exists but SystemTrayDelegate does
not. This code is mid-refactor, sorry.)

Alternately, this object could store the flash_update_available_ boolean, but
you'd still need to call into SystemTrayDelegateChromeOS to trigger showing the
update UI.

 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // chromeos::system::SystemClockObserver:
 
 void SystemTrayClient::OnSystemClockChanged(
     chromeos::system::SystemClock* clock) {
   system_tray_->SetUse24HourClock(clock->ShouldUse24HourClock());
 }