Refactor Uniform validation to validationES.cpp. This patch also incidentally fixes some bugged validation in the new ES3 unsigned int uniform API entry points. BUG=angle:571 Change-Id: I89bd909467bd9418fe5ce3f246561765cf27a5e9 Reviewed-on: https://chromium-review.googlesource.com/200074 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>