Simplify DeferGlobalInitializers It doesn't need to use a traverser, it's simpler to just iterate over all statements in the global scope. BUG=angleproject:1966 TEST=angle_unittests, WebGL conformance tests Change-Id: I11200f72842db86be2bcdd11934262da183cc3b4 Reviewed-on: https://chromium-review.googlesource.com/504727 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>