The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a93125b9266ccae55414178523cc529cedf11df7

commit a93125b9266ccae55414178523cc529cedf11df7
Author: Sarah Hu <xiaoyinh@chromium.org>
Date: Mon Oct 30 19:18:18 2017

Adding ripple effects for touch targets in the views-based lockscreen.

Create LoginButton class as a base class for touch targets to enable
ripple effects.
This CL adds ripple to the following touch targets:
1. Dropdown menu button.
2. Submit button.
3. Pin keyboard button.

Bug:  778740 
Change-Id: Ifd856da4ada342d94511fd2ead11933468fa8750
Reviewed-on: https://chromium-review.googlesource.com/739960
Commit-Queue: Xiaoyin Hu <xiaoyinh@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512572}
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/BUILD.gn
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_bubble.cc
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_bubble.h
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_bubble_unittest.cc
[add] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_button.cc
[add] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_button.h
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_password_view.cc
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_password_view.h
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_pin_view.cc
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_pin_view_unittest.cc
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_user_view.cc
[modify] https://crrev.com/a93125b9266ccae55414178523cc529cedf11df7/ash/login/ui/login_user_view.h