Overview Tray Button should not be visible on login screen

ash/system/overview/overview_button_tray.cc

Index: ash/system/overview/overview_button_tray.cc
diff --git a/ash/system/overview/overview_button_tray.cc b/ash/system/overview/overview_button_tray.cc
index 4ca41668d8f050713dab76be5f83bf45806d7add..edcf6e5487cc7256205ef1d273eb95266046fa13 100644
--- a/ash/system/overview/overview_button_tray.cc
+++ b/ash/system/overview/overview_button_tray.cc
@@ -6,6 +6,7 @@
 
 #include "ash/shelf/shelf_types.h"
 #include "ash/shell.h"
+#include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/tray_utils.h"
 #include "ash/wm/overview/window_selector_controller.h"
 #include "grit/ash_resources.h"
@@ -41,7 +42,8 @@ OverviewButtonTray::OverviewButtonTray(
   SetIconBorderForShelfAlignment();
   tray_container()->AddChildView(icon_);
 
-  SetVisible(Shell::GetInstance()->IsMaximizeModeWindowManagerEnabled());
+  UpdateIconVisibility(Shell::GetInstance()->
+      IsMaximizeModeWindowManagerEnabled());
 
   Shell::GetInstance()->AddShellObserver(this);
 }
@@ -50,17 +52,25 @@ OverviewButtonTray::~OverviewButtonTray() {
   Shell::GetInstance()->RemoveShellObserver(this);
 }
 
+void OverviewButtonTray::UpdateAfterLoginStatusChange(
+    user::LoginStatus status) {
+  UpdateIconVisibility(Shell::GetInstance()->
+      IsMaximizeModeWindowManagerEnabled());
+}
+
 bool OverviewButtonTray::PerformAction(const ui::Event& event) {
   Shell::GetInstance()->window_selector_controller()->ToggleOverview();
   return true;
 }
 
 void OverviewButtonTray::OnMaximizeModeStarted() {
-  SetVisible(true);
+  // TODO(flackr): once maximize mode has been refactored remove this so that
+  // UpdateIconVisibility polls Shell for the status directly
+  UpdateIconVisibility(/* maximize_mode_enabled */ true);
 }
 
 void OverviewButtonTray::OnMaximizeModeEnded() {
-  SetVisible(false);
+  UpdateIconVisibility(/* maximize_mode_enabled */ false);
 }
 
 bool OverviewButtonTray::ClickedOutsideBubble() {
@@ -103,4 +113,9 @@ void OverviewButtonTray::SetIconBorderForShelfAlignment() {
   }
 }
 
+void OverviewButtonTray::UpdateIconVisibility(bool maximize_mode_enabled) {
+  SetVisible(maximize_mode_enabled &&
+             Shell::GetInstance()->window_selector_controller()->CanSelect());
+}
+
 }  // namespace ash