Introduce concurrent on-stack replacement.

src/deoptimizer.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 244 matching lines @@
   static void RevertInterruptCodeAt(Code* unoptimized_code,
                                     Address pc_after,
                                     Code* interrupt_code);
 
 #ifdef DEBUG
   static InterruptPatchState GetInterruptPatchState(Isolate* isolate,
                                                     Code* unoptimized_code,
                                                     Address pc_after);
 
   // Verify that all back edges of a certain loop depth are patched.
-  static void VerifyInterruptCode(Isolate* isolate,
+  static bool VerifyInterruptCode(Isolate* isolate,
                                   Code* unoptimized_code,
                                   int loop_nesting_level);
 #endif  // DEBUG
 
   ~Deoptimizer();
 
   void MaterializeHeapObjects(JavaScriptFrameIterator* it);
 #ifdef ENABLE_DEBUGGER_SUPPORT
   void MaterializeHeapNumbersForDebuggerInspectableFrame(
       Address parameters_top,
@@ skipping 728 matching lines @@
   Object** expression_stack_;
   int source_position_;
 
   friend class Deoptimizer;
 };
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_DEOPTIMIZER_H_