ES31: Implement getMultisamplefv for D3D part. Implement getMultisamplefv for d3d part.Because standard D3D sample positions from https://msdn.microsoft.com/en-us/library/windows/ desktop/ff476218.aspx are fixed sample pattern,we put the sample positions into a constant array in renderer11_utils.cpp with a function to query it. BUG=angleproject:1590 TEST=dEQP-GLES31.functional.texture.multisample.samples_*.sample_position Change-Id: I6e6006ed1c4e22fe006522e9ffd3297247bee75e Reviewed-on: https://chromium-review.googlesource.com/594970 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>