Turn FrontendInputFile into an immutable class and have it also accept
a memory buffer instead of only a filename.

llvm-svn: 167627
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 896e581..9e7b630 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -600,9 +600,9 @@
                                                FileManager &FileMgr,
                                                SourceManager &SourceMgr,
                                                const FrontendOptions &Opts) {
-  StringRef InputFile = Input.File;
+  StringRef InputFile = Input.getFile();
   SrcMgr::CharacteristicKind
-    Kind = Input.IsSystem ? SrcMgr::C_System : SrcMgr::C_User;
+    Kind = Input.isSystem() ? SrcMgr::C_System : SrcMgr::C_User;
 
   // Figure out where to get and map in the main file.
   if (InputFile != "-") {