clang/win: Don't pass -Wno-inconsistent-missing-override twice.

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 812 matching lines @@
       "-Wno-sometimes-uninitialized",
       "-Wno-switch",
       "-Wno-tautological-compare",
       "-Wno-unknown-pragmas",
       "-Wno-unsequenced",
       "-Wno-unused-function",
       "-Wno-unused-private-field",
       "-Wno-unused-value",
       "-Wno-unused-variable",
       "-Wno-unused-local-typedef",  # http://crbug.com/411648
-      "-Wno-inconsistent-missing-override",  #http://crbug.com/428099
     ]
   }
 } else {
   # Common GCC warning setup.
   default_warning_flags += [
     # Enables.
     "-Wendif-labels",  # Weird old-style text after an #endif.
     "-Werror",  # Warnings as errors.
 
     # Disables.
@@ skipping 86 matching lines @@
     # TODO(thakis): Remove, http://crbug.com/263960
     "-Wno-reserved-user-defined-literal",
   ]
 
   # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
   # always have different versions. Certain flags may not be recognized by
   # one version or the other.
   if (!is_nacl) {
     # Flags NaCl does not recognize.
     default_warning_flags += [
-      # TODO(hans): Get this cleaned up.
+      # TODO(hans): Get this cleaned up, http://crbug.com/428099
       "-Wno-inconsistent-missing-override",
     ]
   }
 }
 
 # chromium_code ---------------------------------------------------------------
 #
 # Toggles between higher and lower warnings for code that is (or isn't)
 # part of Chromium.
 
@@ skipping 296 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }