cros: Fix startup page focus

- Move RestoreFocus from BrowserView::Show to OnWidgetActivationChanged
  to do it when the browser window is activated;
- Remove SetInitialFocus in SessionRestoreImpl::ShowBrowser since
  BrowserView change should do that as part of RestoreFocus;
- Also remove the debugging code for SetInitialFocus crash
  under SessionRestoreImpl::RestoreTab since ShowBrowser no longer
  calls SetInitialFocus;

Bug: 859257, 850626, 908524
Change-Id: Ia24e4d68e1386de84765f914bb75319c9887dfd1
Reviewed-on: https://chromium-review.googlesource.com/c/1313728
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614364}
9 files changed