Fix data race with interface caching

src/interface.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERFACE_H_
 #define V8_INTERFACE_H_
 
 #include "src/ast-value-factory.h"
 #include "src/zone-inl.h"  // For operator new.
 
@@ skipping 23 matching lines @@
 
 class Interface : public ZoneObject {
  public:
   // ---------------------------------------------------------------------------
   // Factory methods.
 
   static Interface* NewUnknown(Zone* zone) {
     return new(zone) Interface(NONE);
   }
 
-  static Interface* NewValue() {
-    static Interface value_interface(VALUE + FROZEN);  // Cached.
-    return &value_interface;
-  }
+  static Interface* NewValue();
 
-  static Interface* NewConst() {
-    static Interface value_interface(VALUE + CONST + FROZEN);  // Cached.
-    return &value_interface;
-  }
+  static Interface* NewConst();
 
   static Interface* NewModule(Zone* zone) {
     return new(zone) Interface(MODULE);
   }
 
   // ---------------------------------------------------------------------------
   // Mutators.
 
   // Add a name to the list of exports. If it already exists, unify with
   // interface, otherwise insert unless this is closed.
@@ skipping 108 matching lines @@
 
   // ---------------------------------------------------------------------------
   // Debugging.
 #ifdef DEBUG
   void Print(int n = 0);  // n = indentation; n < 0 => don't print recursively
 #endif
 
   // ---------------------------------------------------------------------------
   // Implementation.
  private:
+  struct ValueCreate;
+  struct ConstCreate;
+
   enum Flags {    // All flags are monotonic
     NONE = 0,
     VALUE = 1,    // This type describes a value
     CONST = 2,    // This type describes a constant
     MODULE = 4,   // This type describes a module
     FROZEN = 8    // This type is fully determined
   };
 
   int flags_;
   Interface* forward_;     // Unification link
@@ skipping 19 matching lines @@
   }
 
   void DoAdd(const void* name, uint32_t hash, Interface* interface, Zone* zone,
              bool* ok);
   void DoUnify(Interface* that, bool* ok, Zone* zone);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_INTERFACE_H_