Add Syzygy support to Windows GN build.

build/config/BUILD.gn

 # Copyright (c) 2013 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/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
+import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//build/module_args/v8.gni")
 
 declare_args() {
   # When set, turns off the (normally-on) iterator debugging and related stuff
   # that is normally turned on for Debug builds. These are generally useful for
   # catching bugs but in some cases may cause conflicts or excessive slowness.
   disable_iterator_debugging = false
 
   # Set to true to not store any build metadata, e.g. ifdef out all __DATE__
@@ skipping 249 matching lines @@
     defines += [ "GOOGLE_CHROME_BUILD" ]
   } else {
     defines += [ "CHROMIUM_BUILD" ]
   }
   if (enable_media_router) {
     defines += [ "ENABLE_MEDIA_ROUTER=1" ]
   }
   if (enable_webvr) {
     defines += [ "ENABLE_WEBVR" ]
   }
+  if (is_syzyasan) {
+    defines += [
+      "SYZYASAN",
+      "MEMORY_TOOL_REPLACES_ALLOCATOR",
+      "MEMORY_SANITIZER_INITIAL_SIZE",
+    ]
+  }
 }
 
 # Debug/release ----------------------------------------------------------------
 
 config("debug") {
   defines = [
     "_DEBUG",
     "DYNAMIC_ANNOTATIONS_ENABLED=1",
     "WTF_USE_DYNAMIC_ANNOTATIONS=1",
   ]
@@ skipping 132 matching lines @@
 
     # This is a file that GN will compile with the above header. It will be
     # implicitly added to the sources (potentially multiple times, with one
     # variant for each language used in the target).
     precompiled_source = "//build/precompile.cc"
 
     # Force include the header.
     cflags = [ "/FI$precompiled_header" ]
   }
 }