Remove Renderer pointer from FBO attachments. Removing the Renderer pointer is one step towards making FBO attachments a minimal state object. Eventually we will be able to store them as arrays instead of arrays of pointers. BUG=angle:660 Change-Id: Idce34e06c339ecb18c60fef12d2ed911d0c4e0f6 Reviewed-on: https://chromium-review.googlesource.com/201835 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org>