[Remarks] Fix mismatched delete due to missing virtual destructor

This fixes an asan failure introduced in r356519.

llvm-svn: 356583
diff --git a/llvm/lib/Remarks/RemarkParserImpl.h b/llvm/lib/Remarks/RemarkParserImpl.h
index 6804657..b4c106b 100644
--- a/llvm/lib/Remarks/RemarkParserImpl.h
+++ b/llvm/lib/Remarks/RemarkParserImpl.h
@@ -19,6 +19,10 @@
 struct ParserImpl {
   enum class Kind { YAML };
 
+  explicit ParserImpl(Kind TheParserKind) : ParserKind(TheParserKind) {}
+  // Virtual destructor prevents mismatched deletes
+  virtual ~ParserImpl() {}
+
   // The parser kind. This is used as a tag to safely cast between
   // implementations.
   Kind ParserKind;