These are copied from chromium's modified eglplatform.h. It is necessary
in order to build ANGLE for freon Chrome OS boards because X11 headers
aren't included in the SDK.

BUG=504501
TEST=cros chrome-sdk --board link
  gclient runhooks
  ninja -C out_link/Release chromium_builder_tests

Change-Id: I37c3cba280689ec8d8a13e8946b1401d4bba7ea8
Reviewed-on: https://chromium-review.googlesource.com/281992Tested-by: Michael Spang <spang@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>