Connect the LocalDB to TabManager.

Bug: 773382
Change-Id: Iec8fe5226ee175105d51f300f30b4865478ac099
Reviewed-on: https://chromium-review.googlesource.com/1118611
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572871}
   TabManagerTest()
       : scoped_context_(
            std::make_unique<base::TestMockTimeTaskRunner::ScopedContext>(
                task_runner_)),
        scoped_set_tick_clock_for_testing_(task_runner_->GetMockTickClock()) {
    base::MessageLoopCurrent::Get()->SetTaskRunner(task_runner_);
  }

   TabManagerTest()
       : scoped_context_(
            std::make_unique<base::TestMockTimeTaskRunner::ScopedContext>(
                task_runner_)),
        scoped_set_tick_clock_for_testing_(task_runner_->GetMockTickClock()) {
    base::MessageLoopCurrent::Get()->SetTaskRunner(task_runner_);
  }
