Fix FreeList::zapFreedMemory to fail "use-of-uninitialized-value" on MSAN

Source/wtf/AddressSanitizer.h

Index: Source/wtf/AddressSanitizer.h
diff --git a/Source/wtf/AddressSanitizer.h b/Source/wtf/AddressSanitizer.h
index bd333708278af859bfb221b16771889faa107a9e..59ccfc1e061e8a1c2cd324aeb92269252003a44b 100644
--- a/Source/wtf/AddressSanitizer.h
+++ b/Source/wtf/AddressSanitizer.h
@@ -4,6 +4,8 @@
 
 #ifndef WTF_AddressSanitizer_h
 #define WTF_AddressSanitizer_h
+// TODO(kojii): This file will need to be renamed, because it's no more
+// specific to AddressSanitizer.
 
 // TODO(sof): Add SyZyASan support?
 #if defined(ADDRESS_SANITIZER)
@@ -22,6 +24,10 @@
 #define __lsan_unregister_root_region(addr, size) ((void)(addr), (void)(size))
 #endif
 
+#if defined(MEMORY_SANITIZER)
+#include <sanitizer/msan_interface.h>
+#endif
+
 // TODO(sof): Have to handle (ADDRESS_SANITIZER && _WIN32) differently as it
 // uses both Clang (which supports the __attribute__ syntax) and CL (which doesn't)
 // as long as we use "clang-cl /fallback". This shouldn't be needed when Clang
@@ -38,4 +44,10 @@
 #define NO_LAZY_SWEEP_SANITIZE_ADDRESS
 #endif
 
+#if defined(MEMORY_SANITIZER) && (!OS(WIN) || COMPILER(CLANG))
+#define NO_SANITIZE_MEMORY __attribute__((no_sanitize_memory))
+#else
+#define NO_SANITIZE_MEMORY
+#endif
+
 #endif // WTF_AddressSanitizer_h