SwapChain11: Create SRV copy texture lazily. We would allocate this texture for devices that don't need it. Instead do this lazily. This was showing up in the profiles for the MotionMark benchmark, possibly due to re-creating the surface. BUG=angleproject:1155 Change-Id: I28b5eda29e21899fc8afef054e1b8063e3cc2e00 Reviewed-on: https://chromium-review.googlesource.com/655479 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>