Fixed issue which caused AssistantOptInView to be painted wrong.

I was unable to repro the bug consistently with an unaltered build.
I was able to repro the bug, however, with some local changes in which
I posted the UpdateLabel calls to simulate a timing issue. With this
change, I was able to reproduce the bug consistently.

Bug: b:130758812
Change-Id: I063527e9c52f5584104ce556d3558fc4ed62e228
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577494Reviewed-by: Tao Wu <wutao@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#652883}

ash/assistant/ui/main_stage/assistant_opt_in_view.cc

@@ -181,6 +181,12 @@ void AssistantOptInView::UpdateLabel(mojom::ConsentStatus consent_status) {
       CreateStyleInfo(gfx::Font::Weight::BOLD));
 
   container_->SetAccessibleName(label_text);
+
+  // After updating the |label_| we need to ensure that it is remeasured and
+  // repainted to address a timing bug in which the AssistantOptInView was
+  // sometimes drawn in an invalid state (b/130758812).
+  container_->Layout();
+  container_->SchedulePaint();
 }
 
 }  // namespace ash