[libFuzzer] don't clear Counters in TracePC::CollectFeatures since they will be cleared anyway in ResetMaps

llvm-svn: 297783
diff --git a/llvm/lib/Fuzzer/FuzzerValueBitMap.h b/llvm/lib/Fuzzer/FuzzerValueBitMap.h
index 600337a..8f7ff74 100644
--- a/llvm/lib/Fuzzer/FuzzerValueBitMap.h
+++ b/llvm/lib/Fuzzer/FuzzerValueBitMap.h
@@ -76,7 +76,7 @@
 
   template <class Callback>
   ATTRIBUTE_NO_SANITIZE_ALL
-  void ForEach(Callback CB) {
+  void ForEach(Callback CB) const {
     for (size_t i = 0; i < kMapSizeInWords; i++)
       if (uintptr_t M = Map[i])
         for (size_t j = 0; j < sizeof(M) * 8; j++)