Timeline: details view UI polish

- move record type title to the left of all tabs and make it bold;
- select last tab by default, unless user have made an explicit choice;
- reduce font for paint profiler pie chart to make total duration
    fit one line.

R=pfeldman,loislo

Review URL: https://codereview.chromium.org/579293002

git-svn-id: svn://svn.chromium.org/blink/trunk@182317 bbb929c8-8fbe-4397-9dbb-9b2b20218538