Use the generic heap shim with SyzyASAN.

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/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/features.gni")
@@ skipping 242 matching lines @@
   }
   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",
     ]
   }
   if (!fieldtrial_testing_like_official_build && !is_chrome_branded) {
     defines += [ "FIELDTRIAL_TESTING_ENABLED" ]
   }
 
   # ==============================================
   #   PLEASE DO NOT ADD MORE THINGS TO THIS LIST
   # ==============================================
@@ skipping 214 matching lines @@
       # file doesn't exist, no error will be generated (probably MS tested this
       # case but forgot the other one?). To reproduce this error, do a build,
       # then delete the precompile.c.obj file, then build again.
       cflags_c = [ "/wd4206" ]
     } else if (is_mac) {
       precompiled_header = "build/precompile.h"
       precompiled_source = "//build/precompile.h"
     }
   }
 }