Actually add a useful bit to the comment pre-FIXME

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145809 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index f2c2f43..f48d18c 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -1858,7 +1858,7 @@
 }
 
 void ASTWriter::WriteSubmodules(Module *WritingModule) {
-  // 
+  // Determine the dependencies of our module and each of it's submodules.
   // FIXME: This feels like it belongs somewhere else, but there are no
   // other consumers of this information.
   SourceManager &SrcMgr = PP->getSourceManager();