Reland with a fix for the compilation on Windows.

Our angle_config.h was using "using namespace" in a header as a way to
import symbols to shim Chromium's base. This patch changes this to
import each function separately using "using".

This patch will allow our gpu_test_expectations to compile inside
Chromium on Linux.

BUG=angleproject:1127

Change-Id: I19b97c2a37accc683a35809859c604bcaf3dcc43
Reviewed-on: https://chromium-review.googlesource.com/295150Tested-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>