Devtools Animations: Add buffer and effect selection to animation timeline

This change allows the animation timeline UI to consume the visual effect
information from the backend models. It pulls these effects into a buffer
and allows each effect to be selected to be displayed in the timeline below.
The scrubber is also disabled for now in this change.

BUG=447083

Review URL: https://codereview.chromium.org/1218433007

git-svn-id: svn://svn.chromium.org/blink/trunk@202665 bbb929c8-8fbe-4397-9dbb-9b2b20218538
8 files changed
tree: cc6ace48a4d3b4c7fde6a347e74f0ee53576c7d5
  1. third_party/