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 574 matching lines @@
   static const int kPatchReturnSequenceAddressOffset =
       kJSReturnSequenceLength - kPatchDebugBreakSlotReturnOffset;
   // Distance between the start of the JS return sequence and where the
   // 32-bit displacement of a short call would be. The short call is from
   // SetDebugBreakAtIC from debug-x64.cc.
   static const int kPatchDebugBreakSlotAddressOffset =
       kDebugBreakSlotLength - kPatchDebugBreakSlotReturnOffset;
   static const int kRealPatchReturnSequenceAddressOffset =
       kMoveAddressIntoScratchRegisterInstructionLength - kPointerSize;
 
+  // Return the code target address of the patch debug break slot
+  inline static Address break_address_from_break_address(Address pc);
+
   // One byte opcode for test eax,0xXXXXXXXX.
   static const byte kTestEaxByte = 0xA9;
   // One byte opcode for test al, 0xXX.
   static const byte kTestAlByte = 0xA8;
   // One byte opcode for nop.
   static const byte kNopByte = 0x90;
 
   // One byte prefix for a short conditional jump.
   static const byte kJccShortPrefix = 0x70;
   static const byte kJncShortOpcode = kJccShortPrefix | not_carry;
@@ skipping 976 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_