Plumb SetVisible from ui::Compositor to the DirectRenderer.

This connection got lost when ui::Compositor was switched to using
Display and Surfaces. Restore the connection so that when the root
compositor becomes invisible we drop the backbuffer memory in the
DirectRenderer.

R=piman@chromium.org
TBR=sky
BUG=606056
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel

Review-Url: https://codereview.chromium.org/2238693002
Cr-Commit-Position: refs/heads/master@{#412421}
32 files changed