Allow the cast tray to function as expected when the installed extension is missing API methods.

BUG=489445

Review URL: https://codereview.chromium.org/1145833003

Cr-Commit-Position: refs/heads/master@{#330663}
views::View* TrayCast::CreateTrayView(user::LoginStatus status) {
  CHECK(tray_ == nullptr);
  tray_ = new tray::CastTrayView(this);
  tray_->SetVisible(is_casting_);
  return tray_;
}

views::View* TrayCast::CreateTrayView(user::LoginStatus status) {
  CHECK(tray_ == nullptr);
  tray_ = new tray::CastTrayView(this);
  tray_->SetVisible(is_casting_);
  return tray_;
}
