InstrProf: Simplify some logic by using ArrayRef::slice (NFC)

llvm-svn: 227898
diff --git a/llvm/lib/ProfileData/CoverageMappingReader.cpp b/llvm/lib/ProfileData/CoverageMappingReader.cpp
index 6476d28..1ab2acb 100644
--- a/llvm/lib/ProfileData/CoverageMappingReader.cpp
+++ b/llvm/lib/ProfileData/CoverageMappingReader.cpp
@@ -543,7 +543,7 @@
   auto &R = MappingRecords[CurrentRecord];
   RawCoverageMappingReader Reader(
       R.FunctionName, R.CoverageMapping,
-      makeArrayRef(Filenames.data() + R.FilenamesBegin, R.FilenamesSize),
+      makeArrayRef(Filenames).slice(R.FilenamesBegin, R.FilenamesSize),
       FunctionsFilenames, Expressions, MappingRegions);
   if (auto Err = Reader.read(Record))
     return Err;