This change is pure refactoring. It will make it easier to fix bugs
related to function declarations.

BUG=angleproject:911
BUG=angleproject:1067
BUG=angleproject:1068
TEST=angle_unittests

Change-Id: I031783dc02612d9cf3ff7a9c8291cf8ab33577aa
Reviewed-on: https://chromium-review.googlesource.com/320081
Tryjob-Request: Olli Etuaho <oetuaho@nvidia.com>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>