Serializer enable/disable flags need thread safety.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index b36f4f059332b93b0be6eeea2fc52f9bb0b07b2e..68ae8c3f09e983fcf72a70872d74261da75999b9 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -74,8 +74,8 @@ Operand MacroAssembler::ExternalOperand(ExternalReference target,
                                         Register scratch) {
   if (root_array_available_ && !Serializer::enabled()) {
     intptr_t delta = RootRegisterDelta(target);
-    if (delta != kInvalidRootRegisterDelta && is_int32(delta)) {
-      Serializer::TooLateToEnableNow();
+    if (delta != kInvalidRootRegisterDelta && is_int32(delta) &&
+        Serializer::TrySetPermanentlyDisabled()) {
       return Operand(kRootRegister, static_cast<int32_t>(delta));
     }
   }
@@ -87,8 +87,8 @@ Operand MacroAssembler::ExternalOperand(ExternalReference target,
 void MacroAssembler::Load(Register destination, ExternalReference source) {
   if (root_array_available_ && !Serializer::enabled()) {
     intptr_t delta = RootRegisterDelta(source);
-    if (delta != kInvalidRootRegisterDelta && is_int32(delta)) {
-      Serializer::TooLateToEnableNow();
+    if (delta != kInvalidRootRegisterDelta && is_int32(delta) &&
+        Serializer::TrySetPermanentlyDisabled()) {
       movp(destination, Operand(kRootRegister, static_cast<int32_t>(delta)));
       return;
     }
@@ -106,8 +106,8 @@ void MacroAssembler::Load(Register destination, ExternalReference source) {
 void MacroAssembler::Store(ExternalReference destination, Register source) {
   if (root_array_available_ && !Serializer::enabled()) {
     intptr_t delta = RootRegisterDelta(destination);
-    if (delta != kInvalidRootRegisterDelta && is_int32(delta)) {
-      Serializer::TooLateToEnableNow();
+    if (delta != kInvalidRootRegisterDelta && is_int32(delta) &&
+        Serializer::TrySetPermanentlyDisabled()) {
       movp(Operand(kRootRegister, static_cast<int32_t>(delta)), source);
       return;
     }
@@ -126,8 +126,8 @@ void MacroAssembler::LoadAddress(Register destination,
                                  ExternalReference source) {
   if (root_array_available_ && !Serializer::enabled()) {
     intptr_t delta = RootRegisterDelta(source);
-    if (delta != kInvalidRootRegisterDelta && is_int32(delta)) {
-      Serializer::TooLateToEnableNow();
+    if (delta != kInvalidRootRegisterDelta && is_int32(delta) &&
+        Serializer::TrySetPermanentlyDisabled()) {
       leap(destination, Operand(kRootRegister, static_cast<int32_t>(delta)));
       return;
     }
@@ -143,8 +143,8 @@ int MacroAssembler::LoadAddressSize(ExternalReference source) {
     // It's correctness is ensured by the asserts in the Call
     // instruction below.
     intptr_t delta = RootRegisterDelta(source);
-    if (delta != kInvalidRootRegisterDelta && is_int32(delta)) {
-      Serializer::TooLateToEnableNow();
+    if (delta != kInvalidRootRegisterDelta && is_int32(delta) &&
+        Serializer::TrySetPermanentlyDisabled()) {
       // Operand is leap(scratch, Operand(kRootRegister, delta));
       // Opcodes : REX.W 8D ModRM Disp8/Disp32  - 4 or 7.
       int size = 4;