Devtools Animations: Display keyframes for CSS Animations in inspector

This change displays CSS animation keyframes alongside the associated
animation player in the Animations sidebar pane. No visible changes are
introduced except with the hidden 'Animation Inspection' experiment enabled.

BUG=419269

Review URL: https://codereview.chromium.org/664993002

git-svn-id: svn://svn.chromium.org/blink/trunk@184328 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Cleanup invalidation reason strings

This patch cleans up the reason strings to not have periods. Additionally,
a typo has been fixed in InspectorTraceEvents.

BUG=410701,424451

Review URL: https://codereview.chromium.org/650993004

git-svn-id: svn://svn.chromium.org/blink/trunk@184330 bbb929c8-8fbe-4397-9dbb-9b2b20218538