Serializer enable/disable flags need thread safety.

src/arm/assembler-arm.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 40 matching lines @@
 namespace internal {
 
 // CpuFeatures keeps track of which features are supported by the target CPU.
 // Supported features must be enabled by a CpuFeatureScope before use.
 class CpuFeatures : public AllStatic {
  public:
   // Detect features of the target CPU. Set safe defaults if the serializer
   // is enabled (snapshots must be portable).
   static void Probe();
 
+  // A special case for printing target and features, which we want to do
+  // before initializing the isolate
+  static void SetHintCreatingSnapshot();
+  static void ProbeWithoutIsolate();
+
   // Display target use when compiling.
   static void PrintTarget();
 
   // Display features.
   static void PrintFeatures();
 
   // Check whether a feature is supported by the target CPU.
   static bool IsSupported(CpuFeature f) {
     ASSERT(initialized_);
     return Check(f, supported_);
@@ skipping 16 matching lines @@
     return cross_compile_ == 0;
   }
 
   static bool VerifyCrossCompiling(CpuFeature f) {
     unsigned mask = flag2set(f);
     return cross_compile_ == 0 ||
            (cross_compile_ & mask) == mask;
   }
 
  private:
+  static void Probe(bool serializer_enabled);
+  static bool hint_creating_snapshot_;
+
   static bool Check(CpuFeature f, unsigned set) {
     return (set & flag2set(f)) != 0;
   }
 
   static unsigned flag2set(CpuFeature f) {
     return 1u << f;
   }
 
 #ifdef DEBUG
   static bool initialized_;
@@ skipping 1582 matching lines @@
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_ASSEMBLER_ARM_H_