FlameChart: Make draw function 10 times faster.

1) put all draw sensitive data into separate external arrays
2) mark particular pixel as painted and do not paint other bars if they
hit into the same pixel.

BUG=302913
R=alph@chromium.org

Review URL: https://codereview.chromium.org/25995003

git-svn-id: svn://svn.chromium.org/blink/trunk@159449 bbb929c8-8fbe-4397-9dbb-9b2b20218538