Implement CHROMIUM_copy_texture for D3D11. BUG=angleproject:1356 Change-Id: I70246762411dbeeb3e291e317854139a68d80070 Reviewed-on: https://chromium-review.googlesource.com/339434 Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>