cros-asan: Fix a crash in chromeos asan bots.

chrome/test/pyautolib/asan_stub.c

Index: chrome/test/pyautolib/asan_stub.c
diff --git a/chrome/test/pyautolib/asan_stub.c b/chrome/test/pyautolib/asan_stub.c
index d2184515fbbc03e444a886389040480f8635dba9..9bbd9d1d1d31bfbc3ecc5f3dea25047df6587e68 100644
--- a/chrome/test/pyautolib/asan_stub.c
+++ b/chrome/test/pyautolib/asan_stub.c
@@ -111,6 +111,7 @@ void __asan_before_dynamic_init(const char *module_name) { }
 void __asan_after_dynamic_init() { }
 int __asan_option_detect_stack_use_after_return;
 typedef unsigned long long uptr;
+void __asan_unpoison_memory_region(void const volatile *addr, uptr size) { }
 uptr __asan_stack_malloc_1(uptr size, uptr real_stack) {}
 uptr __asan_stack_malloc_2(uptr size, uptr real_stack) {}
 uptr __asan_stack_malloc_3(uptr size, uptr real_stack) {}