Add the GetActiveRuntime function back into the x64 version of syzyasan_rtl.

syzygy/agent/asan/rtl_impl.cc

 // Copyright 2012 Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 203 matching lines @@
 }
 
 void WINAPI asan_SetOnExceptionCallback(OnExceptionCallback callback) {
   if (callback != nullptr) {
     agent::asan::SetOnExceptionCallback(base::Bind(callback));
   } else {
     agent::asan::ClearOnExceptionCallback();
   }
 }
 
-#ifndef _WIN64
 // Unittesting seam.
 AsanRuntime* WINAPI asan_GetActiveRuntime() {
   return asan_runtime;
 }
 
+#ifndef _WIN64
 void __declspec(naked) asan_SetAllocationFilterFlag() {
   __asm {
     pushad
     pushfd
   }
   asan_runtime->set_allocation_filter_flag(true);
   __asm {
     popfd
     popad
     ret
@@ skipping 13 matching lines @@
   }
 }
 #endif  // !defined _WIN64
 
 int asan_CrashForException(EXCEPTION_POINTERS* exception) {
   DCHECK_NE(static_cast<EXCEPTION_POINTERS*>(nullptr), exception);
   return agent::asan::AsanRuntime::CrashForException(exception);
 }
 
 }  // extern "C"