clang: Disable new warning -Wbitfield-width on the ToT bots.

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")
 import("//build/config/chrome_build.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ skipping 1029 matching lines @@
   if (!is_nacl) {
     # Flags NaCl does not recognize.
     default_warning_flags += [
       # TODO(hans): Get this cleaned up, http://crbug.com/428099
       "-Wno-inconsistent-missing-override",
 
       # TODO(thakis): Enable this, crbug.com/507717
       "-Wno-shift-negative-value",
     ]
   }
+
+  if (exec_script("//tools/clang/scripts/update.py",
+                  [ "--print-revision" ],
+                  "trim string") != "245965-1") {
+    default_warning_flags += [
+      # TODO(thakis): Move this into outer if once clang is rolled far enough
+      # that the pinned clang understands this flag.
+      # TODO(thakis): Consider enabling this?
+      "-Wno-bitfield-width",
+    ]
+  }
 }
 
 # chromium_code ---------------------------------------------------------------
 #
 # Toggles between higher and lower warnings for code that is (or isn't)
 # part of Chromium.
 
 config("chromium_code") {
   if (is_win) {
     cflags = [ "/W4" ]  # Warning level 4.
@@ skipping 351 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }