Add dawn_opengl_registry_dir build override

Bug: b/298194906
Change-Id: I6cc5a86e215ce511e2cd7c702f8f9c59e0891527
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/149180
Auto-Submit: Peng Huang <penghuang@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
diff --git a/scripts/dawn_overrides_with_defaults.gni b/scripts/dawn_overrides_with_defaults.gni
index 317bd07..de4e982 100644
--- a/scripts/dawn_overrides_with_defaults.gni
+++ b/scripts/dawn_overrides_with_defaults.gni
@@ -97,3 +97,7 @@
 if (!defined(dawn_version_file)) {
   dawn_version_file = ""
 }
+
+if (!defined(dawn_opengl_registry_dir)) {
+  dawn_opengl_registry_dir = "${dawn_root}/third_party/khronos/OpenGL-Registry"
+}
diff --git a/src/dawn/native/BUILD.gn b/src/dawn/native/BUILD.gn
index 0fdba1a..b660ec6 100644
--- a/src/dawn/native/BUILD.gn
+++ b/src/dawn/native/BUILD.gn
@@ -107,8 +107,7 @@
     script = "${dawn_root}/generator/opengl_loader_generator.py"
     args = [
       "--gl-xml",
-      rebase_path("${dawn_root}/third_party/khronos/OpenGL-Registry/xml/gl.xml",
-                  root_build_dir),
+      rebase_path("${dawn_opengl_registry_dir}/xml/gl.xml", root_build_dir),
       "--supported-extensions",
       rebase_path("opengl/supported_extensions.json", root_build_dir),
     ]