Require Parent Access Code to change the clock on child session

This CL adds a method to the login data dispatcher that shows the
parent access widget and uses it to only allow parents to change the
clock when there is a child signed in or a child is a device owner.

Bug: 921145
Change-Id: Ifd83760f8b9000576570f85c895d34c76c4c8bb1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621392
Reviewed-by: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Henrique Grandinetti <hgrandinetti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665149}

• ash/login/login_screen_controller.cc[diff]
• ash/login/login_screen_controller.h[diff]
• ash/login/mock_login_screen_client.cc[diff]
• ash/login/mock_login_screen_client.h[diff]
• ash/login/ui/parent_access_view.cc[diff]
• ash/login/ui/parent_access_view.h[diff]
• ash/login/ui/parent_access_view_unittest.cc[diff]
• ash/login/ui/parent_access_widget.cc[diff]
• ash/login/ui/parent_access_widget.h[diff]
• ash/public/cpp/login_screen.h[diff]
• ash/public/interfaces/login_screen.mojom[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service.cc[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service.h[diff]
• chrome/browser/chromeos/child_accounts/parent_access_code/parent_access_service_browsertest.cc[diff]
• chrome/browser/resources/chromeos/set_time_dialog/set_time_browser_proxy.js[diff]
• chrome/browser/resources/chromeos/set_time_dialog/set_time_dialog.html[diff]
• chrome/browser/resources/chromeos/set_time_dialog/set_time_dialog.js[diff]
• chrome/browser/ui/ash/login_screen_client.cc[diff]
• chrome/browser/ui/ash/login_screen_client.h[diff]
• chrome/browser/ui/ash/test_login_screen.cc[diff]
• chrome/browser/ui/ash/test_login_screen.h[diff]
• chrome/browser/ui/webui/chromeos/set_time_ui.cc[diff]
• chrome/common/chrome_features.cc[diff]
• chrome/common/chrome_features.h[diff]
• chrome/test/data/webui/set_time_dialog_browsertest.js[diff]