Serializer enable/disable flags need thread safety.

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index b271fa2a0fdb50adbf02daa4d45ebe394905291a..96d017d522b0a21f672becdafb188880fbf455d4 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -649,10 +649,8 @@ ExternalReferenceDecoder::~ExternalReferenceDecoder() {
   DeleteArray(encodings_);
 }
 
-
-bool Serializer::serialization_enabled_ = false;
-bool Serializer::too_late_to_enable_now_ = false;
-
+SerializationState Serializer::serialization_state_ = SERIALIZER_STATE_DISABLED;
+Mutex Serializer::serialization_mutex_;
 
 class CodeAddressMap: public CodeEventLogger {
  public:
@@ -766,19 +764,28 @@ CodeAddressMap* Serializer::code_address_map_ = NULL;
 
 
 void Serializer::Enable(Isolate* isolate) {
-  if (!serialization_enabled_) {
-    ASSERT(!too_late_to_enable_now_);
-  }
-  if (serialization_enabled_) return;
-  serialization_enabled_ = true;
+  LockGuard<Mutex> lock_guard(&serialization_mutex_);
+  // Check again under the lock.
+  if (enabled()) return;
+
+  ASSERT(!IsPermanentlyDisabled());
+
+  serialization_state_ = SERIALIZER_STATE_ENABLED;
+
   isolate->InitializeLoggingAndCounters();
   code_address_map_ = new CodeAddressMap(isolate);
 }
 
 
 void Serializer::Disable() {
-  if (!serialization_enabled_) return;
-  serialization_enabled_ = false;
+  LockGuard<Mutex> lock_guard(&serialization_mutex_);
+  if (!enabled()) {
+    ASSERT(code_address_map_ == NULL);
+    return;
+  }
+  if (serialization_state_ != SERIALIZER_STATE_PERMANENTLY_DISABLED) {
+    serialization_state_ = SERIALIZER_STATE_DISABLED;
+  }
   delete code_address_map_;
   code_address_map_ = NULL;
 }