Update css3/filters/should-not-have-compositing-layer for FCM.

This test checks if the layer is promoted by checking if compositing
is enabled, which does not work when ForceCompositingMode is turned on.

Instead, have the test dump its composited layer tree, and the results
will show if the filtered image was promoted to a composited layer or
not.

R=enne@chromium.org, senorblanco@chromium.org
BUG=361729

Review URL: https://codereview.chromium.org/228553004

git-svn-id: svn://svn.chromium.org/blink/trunk@171228 bbb929c8-8fbe-4397-9dbb-9b2b20218538