Use a common include for GL headers.

A common place to define required GL includes gives us a nice
point to centralize GL customizations. In the header currently
are the basic GLES headers with extensions, and a define
carried over from desktop GL.

BUG=angle:466

Change-Id: I6fc61947b4514654ec21355a786904eac04656c0
Reviewed-on: https://chromium-review.googlesource.com/204936
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Nicolas Capens <nicolascapens@chromium.org>
diff --git a/src/libEGL/Config.cpp b/src/libEGL/Config.cpp
index 0b47d55..fdc41a9 100644
--- a/src/libEGL/Config.cpp
+++ b/src/libEGL/Config.cpp
@@ -13,10 +13,7 @@
 #include <algorithm>
 #include <vector>
 
-#include <GLES3/gl3.h>
-#include <GLES3/gl3ext.h>
-#include <GLES2/gl2.h>
-#include <GLES2/gl2ext.h>
+#include "angle_gl.h"
 #include <EGL/eglext.h>
 
 #include "common/debug.h"