Only sync attributes used by the current program in RendererGL. Improves draw call overhead of RendererGL. DrawCallPerf_gl: Before: 136973 score After: 153317 score Improvement: 11.932% BUG=angleproject:959 Change-Id: Ib75f6fdd756648e4a07f6e970cda03abbdbcf009 Reviewed-on: https://chromium-review.googlesource.com/275409 Reviewed-by: Kenneth Russell <kbr@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>