Fix x64 android_tools target compile failure.

build/secondary/third_party/android_tools/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/android/rules.gni")
 
 config("cpu_features_include") {
   include_dirs = [ "ndk/sources/android/cpufeatures" ]
 }
 
+config("cpu_features_warnings") {
+  if (is_clang) {
+    # cpu-features.c has few unused functions on x86 b/26403333
+    cflags = [ "-Wno-unused-function" ]
+  }
+}
+
 # This is the GN version of
 # //build/android/ndk.gyp:cpu_features
 source_set("cpu_features") {
   sources = [
     "ndk/sources/android/cpufeatures/cpu-features.c",
   ]
   public_configs = [ ":cpu_features_include" ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
-  configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [
+    "//build/config/compiler:no_chromium_code",
+
+    # Must be after no_chromium_code for warning flags to be ordered correctly.
+    ":cpu_features_warnings",
+  ]
 }
 
 android_java_prebuilt("android_gcm_java") {
   jar_path = "$android_sdk_root/extras/google/gcm/gcm-client/dist/gcm.jar"
 }
 
 android_java_prebuilt("uiautomator_java") {
   jar_path = "$android_sdk/uiautomator.jar"
 }
 
@@ skipping 72 matching lines @@
   ]
   proguard_preprocess = true
   proguard_config = "//third_party/android_tools/proguard.flags"
   jar_path = "$android_sdk_root/extras/google/google_play_services/libproject/google-play-services_lib/libs/google-play-services.jar"
 }
 
 # TODO(jbudorick): Remove this once net_java_test_support no longer needs it.
 android_java_prebuilt("legacy_http_javalib") {
   jar_path = "$android_sdk/optional/org.apache.http.legacy.jar"
 }