Disable -Wextra for all toolchains.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index b80fa16a684dcda2b2c925923b406cff2c9932f0..d64fdccd064edf3fa3279c7ce70c62977a55d60a 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -743,6 +743,17 @@ config("default_warnings") {
         # TODO(hans): Clean this up. Or disable with finer granularity.
         "-Wno-unused-local-typedef",
       ]
+    } else {
+      cflags += [
+        # This warns if a comparison is always true or always false due to
+        # the limited range of the data type, but do not warn for constant
+        # expressions.
+        # Unfortunately, 'char' is signed on some toolchains and unsigned on
+        # others, and there are downsides to forcing it to be one or the other.
+        # Forcing signed makes ARM builds less performant, and Windows builds
+        # fail if we force unsigned.
+        "-Wno-type-limits",
+      ]
     }
     if (gcc_version >= 48) {
       cflags_cc += [