Apply several small micro-optimizations to ValidateDrawElementsCommon * Remove indirection when getting CotextState from Context * Reduce number of branches from 2 to 1 when checking for an InvalidEnum in FromGLEnum<DrawElementsType> * Provide IndexRange constructor which doesn't initialize the member variables * Reduce number of branches to 1 when checking for BasicDrawStateErrors for the fast path * Remove a few branches and reduce math cost during the buffer range check in ValidateDrawElementsCommon Bug: angleproject:2966 Change-Id: Ibdbed8a59ad9d7abce76622e9f507498e67ab997 Reviewed-on: https://chromium-review.googlesource.com/c/1392805 Commit-Queue: Markus Tavenrath <matavenrath@nvidia.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>