Abstract out fetching of break_address in debug mode

src/mips64/assembler-mips64-inl.h

Index: src/mips64/assembler-mips64-inl.h
diff --git a/src/mips64/assembler-mips64-inl.h b/src/mips64/assembler-mips64-inl.h
index 9c6d1573a24bd1e76ca4835d5896f2950fccf530..9007b44703a686bee6552c0ae7a9e4c271243934 100644
--- a/src/mips64/assembler-mips64-inl.h
+++ b/src/mips64/assembler-mips64-inl.h
@@ -184,6 +184,11 @@ Address Assembler::target_address_from_return_address(Address pc) {
 }
 
 
+Address Assembler::break_address_from_return_address(Address pc) {
+  return pc - Assembler::kPatchDebugBreakSlotReturnOffset;
+}
+
+
 Object* RelocInfo::target_object() {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
   return reinterpret_cast<Object*>(Assembler::target_address_at(pc_, host_));