assistant: Stop logo view animation if not drawn

This cl fixes a bug to stop logo view animation when the view is not
drawn.

Bug: 1044320
Test: manual
Change-Id: Ifa8b3f8ae1cf2c66b58ff2ff778599263ade7166
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2015608Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734262}

ash/assistant/ui/logo_view/logo_view_impl.cc

@@ -217,7 +217,7 @@ void LogoViewImpl::OnBoundsChanged(const gfx::Rect& previous_bounds) {
 
 void LogoViewImpl::VisibilityChanged(views::View* starting_from,
                                      bool is_visible) {
-  if (is_visible)
+  if (IsDrawn())
     state_animator_.StartAnimator();
   else
     state_animator_.StopAnimator();