[clang] Adopt new FileManager error-returning APIs

Update the callers of FileManager::getFile and FileManager::getDirectory to handle the new llvm::ErrorOr-returning methods.

Signed-off-by: Harlan Haskins <harlan@apple.com>
llvm-svn: 367616
diff --git a/clang/tools/clang-format/ClangFormat.cpp b/clang/tools/clang-format/ClangFormat.cpp
index 60a7feb..c0c8dc0 100644
--- a/clang/tools/clang-format/ClangFormat.cpp
+++ b/clang/tools/clang-format/ClangFormat.cpp
@@ -117,7 +117,8 @@
                                  SourceManager &Sources, FileManager &Files,
                                  llvm::vfs::InMemoryFileSystem *MemFS) {
   MemFS->addFileNoOwn(FileName, 0, Source);
-  return Sources.createFileID(Files.getFile(FileName), SourceLocation(),
+  auto File = Files.getFile(FileName);
+  return Sources.createFileID(File ? *File : nullptr, SourceLocation(),
                               SrcMgr::C_User);
 }