Update from https://crrev.com/307664

third_party/mesa/BUILD.gn

 # Copyright 2014 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/ui.gni")
 
 config("mesa_headers_config") {
   include_dirs = [ "src/include" ]
   if (use_x11) {
     defines = [ "MESA_EGL_NO_X11_HEADERS" ]
@@ skipping 601 matching lines @@
     "src/src/mesa/x86-64/x86-64.c",
     "src/src/mesa/x86-64/x86-64.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   previous_configs = configs
   configs = []
   configs = [ ":mesa_internal_config" ] + previous_configs
 
+  if (is_clang) {
+    # Mesa triggers some of these Clang warnings.
+    configs -= [ "//build/config/clang:extra_warnings" ]
+  }
+
   cflags = []
 
-  if (is_clang) {
-    cflags += [ "-Wno-absolute-value" ]
-  }
-
   if (is_android && !is_clang) {
     # Disable sincos() optimization to avoid a linker error
     # since Android's math library doesn't have sincos().
     # Either -fno-builtin-sin or -fno-builtin-cos works.
     cflags += [ "-fno-builtin-sin" ]
   }
 
   if (is_win) {
     # Because we're building as a static library
     defines = [ "_GLAPI_NO_EXPORTS" ]
@@ skipping 44 matching lines @@
     if (is_win) {
       defines = [
         "BUILD_GL32",
         "KEYWORD1=GLAPI",
         "KEYWORD2=GLAPIENTRY",
       ]
     }
   }
 }  # !is_android
 # TODO(GYP) Android osmesa_in_lib_dir target.