Add GN build for parts of gpu and ozone.

third_party/khronos/BUILD.gn

Index: third_party/khronos/BUILD.gn
diff --git a/mojo/public/js/bindings/BUILD.gn b/third_party/khronos/BUILD.gn
similarity index 62%
copy from mojo/public/js/bindings/BUILD.gn
copy to third_party/khronos/BUILD.gn
index 0f305e924ec52d3d1b6923ecc012b55a1ac69eac..27cf05cea4abc599560c5495415c0bfb5461b236 100644
--- a/mojo/public/js/bindings/BUILD.gn
+++ b/third_party/khronos/BUILD.gn
@@ -2,9 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("bindings") {
-  sources = [
-    "constants.cc",
-    "constants.h",
+config("khronos_headers") {
+  include_dirs = [
+    ".",
+    "//gpu",  # Contains GLES2/gl2chromium.h
   ]
 }