Remove histogram-only state machine violation

This CL removes a compositing chicken/egg bug that existed only to compute a
histogram. If the histogram is useful, we should find another way to measure it
that doesn't involve violating the state machine.

R=vollick@chromium.org
BUG=343179

Review URL: https://codereview.chromium.org/165263008

git-svn-id: svn://svn.chromium.org/blink/trunk@167150 bbb929c8-8fbe-4397-9dbb-9b2b20218538