Fix LoginScreenControllerNoSessionTest for Unified

This CL fixes ShowSystemTrayOnPrimaryLoginScreen when UnifiedSystemTray
is enabled. A system tray should not SetVisible(true) before
UpdateAfterLoginStatusChange is called.

TEST=LoginScreenControllerNoSessionTest.ShowSystemTrayOnPrimaryLoginScreen
(--enable-features=SystemTrayUnified)
BUG=847104

Change-Id: I2ca02dd55def1385e769f00604cd42281413d8b7
Reviewed-on: https://chromium-review.googlesource.com/1088266
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564924}

ash/system/status_area_widget.cc

@@ -168,6 +168,8 @@ void StatusAreaWidget::UpdateAfterLoginStatusChange(LoginStatus login_status) {
 
   if (system_tray_)
     system_tray_->UpdateAfterLoginStatusChange(login_status);
+  if (unified_system_tray_)
+    unified_system_tray_->UpdateAfterLoginStatusChange();
   logout_button_tray_->UpdateAfterLoginStatusChange();
   overview_button_tray_->UpdateAfterLoginStatusChange(login_status);
 }

ash/system/unified/unified_system_tray.cc

@@ -165,7 +165,6 @@ UnifiedSystemTray::UnifiedSystemTray(Shelf* shelf)
 
   SetInkDropMode(InkDropMode::ON);
   set_separator_visibility(false);
-  SetVisible(true);
 }
 
 UnifiedSystemTray::~UnifiedSystemTray() {
@@ -188,6 +187,11 @@ gfx::Rect UnifiedSystemTray::GetBubbleBoundsInScreen() const {
   return bubble_ ? bubble_->GetBoundsInScreen() : gfx::Rect();
 }
 
+void UnifiedSystemTray::UpdateAfterLoginStatusChange() {
+  SetVisible(true);
+  PreferredSizeChanged();
+}
+
 bool UnifiedSystemTray::PerformAction(const ui::Event& event) {
   if (bubble_)
     CloseBubble();

ash/system/unified/unified_system_tray.h

@@ -47,6 +47,9 @@ class ASH_EXPORT UnifiedSystemTray : public TrayBackgroundView {
   // Return the bounds of the bubble in the screen.
   gfx::Rect GetBubbleBoundsInScreen() const;
 
+  // Updates when the login status of the system changes.
+  void UpdateAfterLoginStatusChange();
+
   // TrayBackgroundView:
   bool PerformAction(const ui::Event& event) override;
   void ShowBubble(bool show_by_click) override;