Abstract out fetching of break_address in debug mode

src/arm/assembler-arm.h

Index: src/arm/assembler-arm.h
diff --git a/src/arm/assembler-arm.h b/src/arm/assembler-arm.h
index e0b89a5d86cc2999b81609946b8f48eb386a9f29..a006a4eed923ffba9c63d0f864b48624f3a4f9d5 100644
--- a/src/arm/assembler-arm.h
+++ b/src/arm/assembler-arm.h
@@ -781,6 +781,9 @@ class Assembler : public AssemblerBase {
   // in the instruction stream that the call will return from.
   INLINE(static Address return_address_from_call_start(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 constant pool on ARM).
   // This is for calls and branches within generated code.
   inline static void deserialization_set_special_target_at(