diff -up chromium-126.0.6478.26/build/config/compiler/BUILD.gn.clang16-buildflag chromium-126.0.6478.26/build/config/compiler/BUILD.gn
--- chromium-126.0.6478.26/build/config/compiler/BUILD.gn.clang16-buildflag	2024-06-02 14:55:55.298242780 +0200
+++ chromium-126.0.6478.26/build/config/compiler/BUILD.gn	2024-06-02 15:04:43.839882669 +0200
@@ -1889,9 +1889,6 @@ config("default_warnings") {
 
         # TODO(crbug.com/40286317): Evaluate and possibly enable.
         "-Wno-vla-extension",
-
-        # TODO(crbug.com/40284799): Fix and re-enable.
-        "-Wno-thread-safety-reference-return",
       ]
 
       cflags_cc += [
@@ -1902,7 +1899,7 @@ config("default_warnings") {
       if (!is_nacl) {
         cflags_cc += [
           # TODO(crbug.com/41486292): Fix and re-enable.
-          "-Wno-c++11-narrowing-const-reference",
+          "-Wno-c++11-narrowing",
         ]
       }
     }