Move optional.h to webrtc/api/

webrtc/test/fuzzers/BUILD.gn

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../../webrtc.gni")
 import("//build/config/features.gni")
@@ skipping 189 matching lines @@
   ]
 }
 
 rtc_static_library("audio_decoder_fuzzer") {
   sources = [
     "audio_decoder_fuzzer.cc",
     "audio_decoder_fuzzer.h",
   ]
   deps = [
     "../..:webrtc_common",
+    "../../api:optional",
     "../../api/audio_codecs:audio_codecs_api",
     "../../modules/rtp_rtcp",
     "../../rtc_base:rtc_base_approved",
   ]
 }
 
 webrtc_fuzzer_test("audio_decoder_ilbc_fuzzer") {
   sources = [
     "audio_decoder_ilbc_fuzzer.cc",
   ]
@@ skipping 142 matching lines @@
   ]
 }
 
 webrtc_fuzzer_test("audio_processing_fuzzer") {
   sources = [
     "audio_processing_fuzzer.cc",
     "audio_processing_fuzzer.h",
     "audio_processing_fuzzer_configs.cc",
   ]
   deps = [
+    "../../api:optional",
     "../../modules:module_api",
     "../../modules/audio_processing",
     "../../rtc_base:rtc_base_approved",
   ]
 }