Specialized Context11 impl to prevent promote Dynamic during MultiDraw. Add different buffer usage to MultiDraw and BaseVertexBaseInstance tests. Bug: angleproject:3402, angleproject:4754 Change-Id: I50e1a6fd6c8b6fd48f130c43545b895335d2e55b Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2268581 Commit-Queue: Shrek Shao <shrekshao@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>
