Port r282246 to gn.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 if (is_posix) {
   import("//build/config/gcc/gcc_version.gni")
@@ skipping 433 matching lines @@
     ]
 
   }
 }
 
 # chromium_code ---------------------------------------------------------------
 #
 # Toggles between higher and lower warnings for code that is (or isn't)
 # part of Chromium.
 
+# TODO: -Werror and /WX should always be on, independent of chromium_code
+# http://crbug.com/393046
 config("chromium_code") {
   if (is_win) {
     cflags = [
       "/W4",  # Warning level 4.
       "/WX",  # Treat warnings as errors.
     ]
   } else {
     cflags = [
       "-Wall",
-      "-Werror",
 
       # GCC turns on -Wsign-compare for C++ under -Wall, but clang doesn't,
       # so we specify it explicitly.
       # TODO(fischman): remove this if http://llvm.org/PR10448 obsoletes it.
       # http://code.google.com/p/chromium/issues/detail?id=90453
       "-Wsign-compare",
     ]
+    if (!is_linux) {
+      # TODO: Add this unconditionally once linux builds without warnings with
+      # clang in the gn build.
+      cflags += [ "-Werror" ]
+    }
 
     # In Chromium code, we define __STDC_foo_MACROS in order to get the
     # C99 macros on Mac and Linux.
     defines = [
       "__STDC_CONSTANT_MACROS",
       "__STDC_FORMAT_MACROS",
     ]
 
     # TODO(brettw) this should also be enabled on Linux but some files
     # currently fail.
@@ skipping 359 matching lines @@
   } else {
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }