message: Clarify disabled warning for Metal in BUILD.gn
diff: @@ -46,7 +46,11 @@ source_set("dawn_platform") {
  config("libdawn_native_internal") {
  configs = [ "${dawn_root}/src/common:dawn_internal" ]
  - # Suppress warnings that Metal isn't in the deployment target of Chrome
  + # Suppress warnings that Metal isn't in the deployment target of Chrome:
  + # initialization of the Metal backend is behind a IsMetalSupported check so
  + # Dawn won't call Metal functions on macOS 10.10.
  + # TODO(cwallez@chromium.org): Consider using API_AVAILABLE annotations on all
  + # metal code in dawn once crbug.com/1004024 is sorted out.
  if (is_mac) {
  cflags_objcc = [ "-Wno-unguarded-availability" ]
  }
  