Split FileEntry name vs. isValid

This is a small bit of refactoring in preparation for FileEntry owning
the storage for its own name.

llvm-svn: 202412
diff --git a/clang/lib/Frontend/TextDiagnostic.cpp b/clang/lib/Frontend/TextDiagnostic.cpp
index a2dc953..79f05c6 100644
--- a/clang/lib/Frontend/TextDiagnostic.cpp
+++ b/clang/lib/Frontend/TextDiagnostic.cpp
@@ -787,7 +787,7 @@
     FileID FID = SM.getFileID(Loc);
     if (!FID.isInvalid()) {
       const FileEntry* FE = SM.getFileEntryForID(FID);
-      if (FE && FE->getName()) {
+      if (FE && FE->isValid()) {
         OS << FE->getName();
         if (FE->isInPCH())
           OS << " (in PCH)";