Remove capture notification when on user changed

This bug is caused by the screen capture notification in the message
center when switching to a different user. In this cl this notification
is removed when on user switched.

Bug: 1176154

(cherry picked from commit eeb1596)

Change-Id: I85edcf42eaf6f08f32863c4c9b42191e8b5e81ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2730853
Reviewed-by: Ahmed Mehfooz <amehfooz@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Jiaming Cheng <jiamingc@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#859543}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2733656
Cr-Commit-Position: refs/branch-heads/4430@{#244}
Cr-Branched-From: e5ce7dc-refs/heads/master@{#857950}

ash/capture_mode/capture_mode_controller.cc

@@ -540,6 +540,11 @@ void CaptureModeController::OnRecordingEnded(bool success) {
 void CaptureModeController::OnActiveUserSessionChanged(
     const AccountId& account_id) {
   EndSessionOrRecording(EndRecordingReason::kActiveUserChange);
+
+  // Remove the previous notification when switching to another user.
+  auto* message_center = message_center::MessageCenter::Get();
+  message_center->RemoveNotification(kScreenCaptureNotificationId,
+                                     /*by_user=*/false);
 }
 
 void CaptureModeController::OnSessionStateChanged(