DevTools: make the fading curve nicer for DOM update highlight.

Review URL: https://codereview.chromium.org/723533002

git-svn-id: svn://svn.chromium.org/blink/trunk@185211 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: dom nodes rendered in console have huge margins

BUG=432104

Review URL: https://codereview.chromium.org/711383002

git-svn-id: svn://svn.chromium.org/blink/trunk@185215 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: instant events should not overlap on Timeline flame chart when zooming in

Instant events are now considered as having duration 1us rather than 10us which makes overlapping much less likely.

BUG=398783

Review URL: https://codereview.chromium.org/721703002

git-svn-id: svn://svn.chromium.org/blink/trunk@185217 bbb929c8-8fbe-4397-9dbb-9b2b20218538