[llvm-cov] Document a few private fields of CodeCoverageTool (NFC)

llvm-svn: 275639
diff --git a/llvm/tools/llvm-cov/CodeCoverage.cpp b/llvm/tools/llvm-cov/CodeCoverage.cpp
index ed48c28..59cb708 100644
--- a/llvm/tools/llvm-cov/CodeCoverage.cpp
+++ b/llvm/tools/llvm-cov/CodeCoverage.cpp
@@ -101,11 +101,14 @@
   std::string CoverageArch;
 
 private:
+  /// File paths (absolute, or otherwise) to input source files.
   std::vector<std::string> CollectedPaths;
 
+  /// Errors and warnings which have not been printed.
   std::mutex DeferredMessagesLock;
   std::vector<std::string> DeferredMessages;
 
+  /// A container for input source file buffers.
   std::mutex LoadedSourceFilesLock;
   std::vector<std::pair<std::string, std::unique_ptr<MemoryBuffer>>>
       LoadedSourceFiles;