Assert when building Asan on windows in debug mode

build/config/sanitizers/sanitizers.gni

 # Copyright 2015 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/chrome_build.gni")
 import("//build/toolchain/toolchain.gni")
 
 declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
@@ skipping 166 matching lines @@
 # this condition. We may also be able to find another way to enable your case
 # without having people accidentally get broken builds by compiling an
 # unsupported or unadvisable configurations.
 #
 # For one-off testing, just comment this assertion out.
 assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_null || is_ubsan_vptr),
        "Sanitizers should generally be used in release (set is_debug=false).")
 
 assert(!is_msan || (is_linux && current_cpu == "x64"),
        "MSan currently only works on 64-bit Linux and ChromeOS builds.")
+
+# ASAN build on Windows is not working in debug mode. Intercepting memory
+# allocation functions is hard on Windows and not yet implemented in LLVM.
+assert(!is_win || !is_debug || !is_asan,
+       "ASan on Windows doesn't work in debug (set is_debug=false).")