Abstract out fetching of break_address in debug mode

src/x64/assembler-x64.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 520 matching lines @@
                                            ICacheFlushMode icache_flush_mode =
                                                FLUSH_ICACHE_IF_NEEDED) {
     ConstantPoolArray* constant_pool = code ? code->constant_pool() : NULL;
     set_target_address_at(pc, constant_pool, target, icache_flush_mode);
   }
 
   // Return the code target address at a call site from the return address
   // of that call in the instruction stream.
   static inline Address target_address_from_return_address(Address pc);
 
+  // Return the code target address of the patch debug break slot
+  inline static Address break_address_from_return_address(Address pc);
+
   // This sets the branch destination (which is in the instruction on x64).
   // This is for calls and branches within generated code.
   inline static void deserialization_set_special_target_at(
       Address instruction_payload, Code* code, Address target) {
     set_target_address_at(instruction_payload, code, target);
   }
 
   static inline RelocInfo::Mode RelocInfoNone() {
     if (kPointerSize == kInt64Size) {
       return RelocInfo::NONE64;
@@ skipping 1030 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_