Reland "Add time loading reporter for Chrome OS views-based multiprofile"

This reverts commit ca53ea05b3febd348297deb6d2b81edbf0774bee.

Reason for revert: Found a fix for use-after-free error

Original change's description:
> Revert "Add time loading reporter for Chrome OS views-based multiprofile"
> 
> This reverts commit a89614a196d83755c76459947fa9faa1082fa562.
> 
> Reason for revert: Seems to be causing heap-use-after-free failures on Linux ChromiumOS MSan/LSan/TSan builders:
> 
> https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/20296
> 
> https://ci.chromium.org/p/chromium/builders/ci/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20%281%29/38328
> 
> Original change's description:
> > Add time loading reporter for Chrome OS views-based multiprofile
> > 
> > Bug: 1066489
> > Change-Id: Iceeaee0f33dff50d75361d1f14e14299a37a0830
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2292477
> > Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
> > Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
> > Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#800055}
> 
> TBR=antrim@chromium.org,asvitkine@chromium.org,rsorokin@chromium.org,tellier@google.com
> 
> Change-Id: Iaae1e4466b6b5ac06f609efacc2f02398ab27fd2
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1066489
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2367193
> Reviewed-by: Mohsen Izadi <mohsen@chromium.org>
> Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#800171}

TBR=antrim@chromium.org,mohsen@chromium.org,asvitkine@chromium.org,rsorokin@chromium.org,tellier@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1066489
Change-Id: I2ee0bae97dfebd2be6f745088f954e8afdd7688c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377877
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Thomas Tellier <tellier@google.com>
Cr-Commit-Position: refs/heads/master@{#802185}

diff --git a/ash/login/login_screen_controller.cc b/ash/login/login_screen_controller.cc
index 7c0ea91b..4ab581f0 100644
--- a/ash/login/login_screen_controller.cc
+++ b/ash/login/login_screen_controller.cc

@@ -478,4 +478,10 @@
   client_->OnFocusLeavingSystemTray(reverse);
 }
 
+void LoginScreenController::NotifyLoginScreenShown() {
+  if (!client_)
+    return;
+  client_->OnLoginScreenShown();
+}
+
 }  // namespace ash