Re-land "Validate that attrib offsets don't overflow buffers." During draw calls, we wouldn't add the current attrib offset to the required draw call size when checking attributes. This could lead to us producing warnings in the D3D11 runtime, and miss returning some errors. Re-land with a test data initialization fix, and with some extra tests merged from another CL. BUG=angleproject:1339 Change-Id: Ifd549c3b1f6871417dc1693cb3ec534414e92cfd Reviewed-on: https://chromium-review.googlesource.com/333723 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>