Implement drawRangeElements Implement drawRangeElements simply by calling drawElements internally. The start and end parameters passed to the function will be checked against results from index validation and an error is generated if indices fall outside the claimed range. Most dEQP-GLES3.functional.draw.draw_range_elements.* tests pass after this change. The remaining failures seem to be related to instanced attributes. BUG=angleproject:957 TEST=dEQP-GLES3.functional.draw.* Change-Id: Id3923eb8114461b441e593357bc49babfd6b5c15 Reviewed-on: https://chromium-review.googlesource.com/262420 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Olli Etuaho <oetuaho@nvidia.com>