Run-time control enableImageColorProfiles during layout tests

Run-time flag enableImageColorProfiles defaults to off. Add a window
InternalSettings method to enable the flag during layout tests.

BUG=369787

Review URL: https://codereview.chromium.org/643713006

git-svn-id: svn://svn.chromium.org/blink/trunk@184851 bbb929c8-8fbe-4397-9dbb-9b2b20218538