Serializer enable/disable flags need thread safety.

src/arm/assembler-arm.cc

Index: src/arm/assembler-arm.cc
diff --git a/src/arm/assembler-arm.cc b/src/arm/assembler-arm.cc
index 516d3dd57ac3d7a4a282474b0c687ad576d66f53..a463990426994411da13f84fe39e3d6d17d81b70 100644
--- a/src/arm/assembler-arm.cc
+++ b/src/arm/assembler-arm.cc
@@ -1080,9 +1080,7 @@ static bool fits_shifter(uint32_t imm32,
 bool Operand::must_output_reloc_info(const Assembler* assembler) const {
   if (rmode_ == RelocInfo::EXTERNAL_REFERENCE) {
 #ifdef DEBUG

[Sven Panne, 2014/04/16 09:18:46]

Why do we wrap this into #ifdef DEBUG here plus some other places, but not in
ohters? I propose to move any #ifdef logic (if really necessary) into
TrySetPermanentlyDisabled, avoiding the need to repeat this horror at all call
sites (something which we should do in general).

[mvstanton, 2014/04/16 13:43:30]

Thx Sven you got me wondering why we have this call at all. We actually decide
the Enabled/Disabled state at process startup, and we don't toggle it. So this
is superfluous code, removed.

-    if (!Serializer::enabled()) {
-      Serializer::TooLateToEnableNow();
-    }
+    Serializer::TrySetPermanentlyDisabled();
 #endif  // def DEBUG
     if (assembler != NULL && assembler->predictable_code_size()) return true;
     return Serializer::enabled();
@@ -3268,9 +3266,7 @@ void Assembler::RecordRelocInfo(const RelocInfo& rinfo) {
     // Don't record external references unless the heap will be serialized.
     if (rinfo.rmode() == RelocInfo::EXTERNAL_REFERENCE) {
 #ifdef DEBUG
-      if (!Serializer::enabled()) {
-        Serializer::TooLateToEnableNow();
-      }
+      Serializer::TrySetPermanentlyDisabled();
 #endif
       if (!Serializer::enabled() && !emit_debug_code()) {
         return;