Update some comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168400 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 5adf090..0582635 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -316,7 +316,8 @@
   // table for the same directory as DW_at_comp_dir.
   StringRef CompilationDir;
 
-  // A holder for the DarwinGDBCompat flag so that the compile unit can use it.
+  // Holders for the various debug information flags that we might need to
+  // have exposed. See accessor functions below for description.
   bool isDarwinGDBCompat;
   bool hasDwarfAccelTables;
   bool hasDwarfFission;