Use a MutableArrayRef. NFC.

llvm-svn: 305968
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 53cdaac..8ccdd3f 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -732,8 +732,8 @@
         uint64_t FixedValue;
         bool IsPCRel;
         std::tie(FixedValue, IsPCRel) = handleFixup(Layout, Frag, Fixup);
-        getBackend().applyFixup(Fixup, Contents.data(), Contents.size(),
-                                FixedValue, IsPCRel, getContext());
+        getBackend().applyFixup(Fixup, Contents, FixedValue, IsPCRel,
+                                getContext());
       }
     }
   }