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..7a4228559004706e375d93e339f30667fdae2446 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -529,7 +529,6 @@ config("chromium_code") {
   } else {
     cflags = [
       "-Wall",
-      "-Wextra",
 
       # GCC turns on -Wsign-compare for C++ under -Wall, but clang doesn't,
       # so we specify it explicitly.
@@ -743,6 +742,17 @@ 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 += [