rtc::Optional: Tell sanitizers that unset values aren't OK to access

webrtc/base/optional.cc

 /*
  *  Copyright 2016 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.
  */
 
-#include "webrtc/base/logging.h"
-
-#import <Foundation/Foundation.h>
-
+#include "webrtc/base/optional.h"
 
 namespace rtc {
-std::string DescriptionFromOSStatus(OSStatus err) {
-  NSError* error =
-      [NSError errorWithDomain:NSOSStatusErrorDomain code:err userInfo:nil];
-  return error.description.UTF8String;
-}
+namespace internal {
+
+#if RTC_HAS_ASAN
+
+void* FunctionThatDoesNothingImpl(void* x) { return x; }
+
+#endif
+
+}  // namespace internal
 }  // namespace rtc