GitLab

Please refer to https://carbon.googleplex.com/cros-ux/pages/screen-capture/motion#647b61a3-343c-448d-8c9b-f289d357c615
for the spec (search for "Screen record countdown").

Not covered in this CL:
- stop-recording shelf item animation

Bug: 1126669
Change-Id: I747f7df5f51677ef263921f5f00aa56f540b023b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463646Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Xiaoqian Dai <xdai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818529}