This will allow us to pass pointers in the attributes list. This is
helpful for the angle::Platform init code.

Bug: angleproject:2552
Bug: angleproject:2564
Change-Id: I388d907ad543a61f357c0a51e8242942118bdaea
Reviewed-on: https://chromium-review.googlesource.com/1064195Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>