Remove ash/system references from WebUILoginView

Bug: 854346
Test: the new test case
Change-Id: I5a78d4037ffcf2daf995c2fc04ef44459abbd21c
Reviewed-on: https://chromium-review.googlesource.com/c/1338187
Commit-Queue: Jun Mukai <mukai@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612451}

diff --git a/ash/login/login_screen_controller.cc b/ash/login/login_screen_controller.cc
index 1dca8ab..916c0e5b 100644
--- a/ash/login/login_screen_controller.cc
+++ b/ash/login/login_screen_controller.cc

@@ -21,6 +21,7 @@
 #include "ash/system/status_area_widget_delegate.h"
 #include "ash/system/toast/toast_data.h"
 #include "ash/system/toast/toast_manager.h"
+#include "ash/system/tray/system_tray_notifier.h"
 #include "base/bind.h"
 #include "base/debug/alias.h"
 #include "base/strings/string_number_conversions.h"
@@ -59,9 +60,15 @@
 
 }  // namespace
 
-LoginScreenController::LoginScreenController() : weak_factory_(this) {}
+LoginScreenController::LoginScreenController(
+    SystemTrayNotifier* system_tray_notifier)
+    : system_tray_notifier_(system_tray_notifier), weak_factory_(this) {
+  system_tray_notifier_->AddSystemTrayFocusObserver(this);
+}
 
-LoginScreenController::~LoginScreenController() = default;
+LoginScreenController::~LoginScreenController() {
+  system_tray_notifier_->RemoveSystemTrayFocusObserver(this);
+}
 
 // static
 void LoginScreenController::RegisterProfilePrefs(PrefRegistrySimple* registry,
@@ -559,4 +566,10 @@
   }
 }
 
+void LoginScreenController::OnFocusLeavingSystemTray(bool reverse) {
+  if (!login_screen_client_)
+    return;
+  login_screen_client_->OnFocusLeavingSystemTray(reverse);
+}
+
 }  // namespace ash