[Coverage] Mark a few methods const (NFC)

llvm-svn: 275337
diff --git a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
index 2d83320..7303734 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -456,7 +456,7 @@
   return R.Kind == CounterMappingRegion::ExpansionRegion && R.FileID == FileID;
 }
 
-CoverageData CoverageMapping::getCoverageForFile(StringRef Filename) {
+CoverageData CoverageMapping::getCoverageForFile(StringRef Filename) const {
   CoverageData FileCoverage(Filename);
   std::vector<coverage::CountedRegion> Regions;