Still do the actual generation in the Renderer9/11 for now but route it
through the DisplayImpl.

BUG=angle:658

Change-Id: Ib976fbd1b9e349146dc068bbdd4e6a3d2a5ddc69
Reviewed-on: https://chromium-review.googlesource.com/238860Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>