FlameChart: reduce number of arrays in timelineData.

On the next step I'd change the logic of color processing.

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/184353003

git-svn-id: svn://svn.chromium.org/blink/trunk@168127 bbb929c8-8fbe-4397-9dbb-9b2b20218538