Now that C++11 constructor syntax is allowed, we can use a much
simpler scheme.

BUG=angleproject:1407
BUG=chromium:616176

Change-Id: Ida5f235c3ed1429564af5213a5fead6c3b896080
Reviewed-on: https://chromium-review.googlesource.com/350903Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>