A common place to define required GL includes gives us a nice point to centralize GL customizations. In the header currently are the basic GLES headers with extensions, and a define carried over from desktop GL. BUG=angle:466 Change-Id: I6fc61947b4514654ec21355a786904eac04656c0 Reviewed-on: https://chromium-review.googlesource.com/204936Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Zhenyao Mo <zmo@chromium.org> Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
