cros: Fixes the text input focus when screen is locked.

When the screen is locked after some time not used, the initial text input focus is not in the password field when --enable-text-input-focus-manager is enabled.  This CL fixes this issue and puts the text input focus in the password field of the lock screen.

The issue occurs only when the screen gets locked because of time-out.  When it's explicitly locked by a user, the issue doesn't occur.  Please allow me about not adding a test case because it's tough to add a test case.

BUG=290701
TEST=Done manually.

Review URL: https://codereview.chromium.org/371923002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281727 0039d316-1c4b-4281-b951-d872f2087c98

• chrome/browser/chromeos/login/lock/webui_screen_locker.cc[diff]
• chrome/browser/chromeos/login/ui/lock_window.cc[diff]
• chrome/browser/chromeos/login/ui/lock_window.h[diff]
• chrome/browser/chromeos/login/ui/lock_window_aura.cc[diff]
• chrome/browser/chromeos/login/ui/lock_window_aura.h[diff]