CPUProfiler: convert Flame Chart into Icicle Chart

BUG=
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/205563007

git-svn-id: svn://svn.chromium.org/blink/trunk@170140 bbb929c8-8fbe-4397-9dbb-9b2b20218538