clang/win: Take another stab at building with -Wunused-private-field.

third_party/cld_2/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/features.gni")
 
 gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ rebase_path("cld_2.gyp") ],
                           "scope",
                           [ "cld_2.gyp" ])
@@ skipping 65 matching lines @@
   if (cld2_platform_support == "static") {
     deps += [ ":cld2_static" ]
   } else if (cld2_platform_support == "dynamic") {
     deps += [ ":cld2_dynamic" ]
   }
 }
 
 config("cld2_warnings") {
   if (is_clang) {
     cflags = [
-      # cld_2 has unused private fields.
+      # cld_2 contains unused private fields.
+      # https://code.google.com/p/cld2/issues/detail?id=37
       "-Wno-unused-private-field",
     ]
   }
 }
 
 static_library("cld2_static") {
   sources = gypi_values.cld2_core_impl_sources
   include_dirs = [
     "src/internal",
     "src/public",
@@ skipping 49 matching lines @@
       ":cld2_dynamic",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [
       ":cld2_dynamic_mode_config",
       "//build/config/compiler:no_chromium_code",
     ]
   }
 }