Set initial active browser for X11 avatar menu

This fixes the initial state of the menu, where previously there would be no
check mark next to the active profile and the edit and create profile entries
would be disabled.

R=thestig

Change-Id: I1aebbac6fac657fbcb50324068ac58d5c38dd74d
Bug: 1015759
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869990
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707617}

chrome/browser/ui/views/frame/global_menu_bar_x11.cc

@@ -269,7 +269,8 @@ void GlobalMenuBarX11::Initialize(DbusMenu::InitializedCallback callback) {
   ProfileManager* profile_manager = g_browser_process->profile_manager();
   DCHECK(profile_manager);
   avatar_menu_ = std::make_unique<AvatarMenu>(
-      &profile_manager->GetProfileAttributesStorage(), this, nullptr);
+      &profile_manager->GetProfileAttributesStorage(), this,
+      BrowserList::GetInstance()->GetLastActive());
   avatar_menu_->RebuildMenu();
   BrowserList::AddObserver(this);