capture_mode: Do not show feature pod in lock/login screen.

This CL removes the feature pod on lock/login screen.

R=shidi

Test: Manually tested on DUT.
Bug: 1134315
Change-Id: I6afea7f835989fa1147e5d70d5cf770b185d441b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2503831Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Judy Wang <shidi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825385}

ash/capture_mode/capture_mode_feature_pod_controller.cc

@@ -7,6 +7,8 @@
 #include "ash/capture_mode/capture_mode_controller.h"
 #include "ash/capture_mode/capture_mode_metrics.h"
 #include "ash/resources/vector_icons/vector_icons.h"
+#include "ash/session/session_controller_impl.h"
+#include "ash/shell.h"
 #include "ash/strings/grit/ash_strings.h"
 #include "ash/system/tray/system_tray_item_uma_type.h"
 #include "ash/system/unified/feature_pod_button.h"
@@ -23,6 +25,8 @@ FeaturePodButton* CaptureModeFeaturePodController::CreateButton() {
   button_->SetVectorIcon(kCaptureModeIcon);
   button_->SetLabel(
       l10n_util::GetStringUTF16(IDS_ASH_STATUS_TRAY_CAPTURE_MODE_BUTTON_LABEL));
+  button_->SetVisible(
+      !Shell::Get()->session_controller()->IsUserSessionBlocked());
   return button_;
 }