Adds a Framebuffer class to encapsulate and abstract framebuffer creation with or without multisampling. Bug: b/158231104 Change-Id: I4198f53f872aae76955ba13f1f2372067b91a07c Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45789 Presubmit-Ready: Nicolas Capens <nicolascapens@google.com> Tested-by: Nicolas Capens <nicolascapens@google.com> Kokoro-Result: kokoro <noreply+kokoro@google.com> Reviewed-by: Antonio Maiorano <amaiorano@google.com>
