Introduce SynchronizedScope to allow heap access from compiler thread.

src/compiler.h

 // Copyright 2012 the V8 project authors. 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.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 230 matching lines @@
   }
 
   // Determines whether or not to insert a self-optimization header.
   bool ShouldSelfOptimize();
 
   void set_deferred_handles(DeferredHandles* deferred_handles) {
     ASSERT(deferred_handles_ == NULL);
     deferred_handles_ = deferred_handles;
   }
 
+  bool is_concurrent() { return deferred_handles_ != NULL; }
+
   ZoneList<Handle<HeapObject> >* dependencies(
       DependentCode::DependencyGroup group) {
     if (dependencies_[group] == NULL) {
       dependencies_[group] = new(zone_) ZoneList<Handle<HeapObject> >(2, zone_);
     }
     return dependencies_[group];
   }
 
   void CommitDependencies(Handle<Code> code);
 
@@ skipping 418 matching lines @@
   unsigned info_zone_start_allocation_size_;
   ElapsedTimer timer_;
 
   DISALLOW_COPY_AND_ASSIGN(CompilationPhase);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_COMPILER_H_