Abstract out fetching of break_address in debug mode

src/mips64/assembler-mips64.h

Index: src/mips64/assembler-mips64.h
diff --git a/src/mips64/assembler-mips64.h b/src/mips64/assembler-mips64.h
index 395ab77d8ace9116fb290d140da7a67d6ab468eb..f59909305b356d0e96d3a39bfdf92830a86e375b 100644
--- a/src/mips64/assembler-mips64.h
+++ b/src/mips64/assembler-mips64.h
@@ -503,6 +503,9 @@ class Assembler : public AssemblerBase {
   // of that call in the instruction stream.
   inline static 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);
+
   static void JumpLabelToJumpRegister(Address pc);
 
   static void QuietNaN(HeapObject* nan);