Address some TODO(GYP)s in the GN build.

ui/resources/BUILD.gn

Index: ui/resources/BUILD.gn
diff --git a/ui/resources/BUILD.gn b/ui/resources/BUILD.gn
index 1b407f3712ffff3582911bdc94b7a14bea6099c4..fb5783c9cde6e8fe0624c05bdfa368f6a6d2c2a5 100644
--- a/ui/resources/BUILD.gn
+++ b/ui/resources/BUILD.gn
@@ -31,6 +31,11 @@ grit("ui_unscaled_resources_grd") {
   use_qualified_include = true
   outputs = [
     "grit/ui_unscaled_resources.h",
+
+    # TODO(GYP_GONE) when GYP is gone, this line should be deleted, and the grit
+    # file updated to no longer list this as an output. We use resource bundles
+    # rather than .rc files, but the GYP build still expects this file to
+    # exist.
     "ui_unscaled_resources.rc",
   ]
 }