Using x = {}; before filling out each field, we can be sure any missing
field is 0 initialized.  This in turn helps us not have to specify
certain fields that are generally unused (at the moment), such
as pNext.

Bug: angleproject:2860
Change-Id: Ia1fa2db3ecfb316673a02ac0c5e13e47e055a19f
Reviewed-on: https://chromium-review.googlesource.com/c/1259764Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>