[pdb] Round trip the PDB stream between YAML and binary PDB.

This gets writing of the PDB stream working.

llvm-svn: 274647
diff --git a/llvm/lib/DebugInfo/PDB/Raw/TpiStream.cpp b/llvm/lib/DebugInfo/PDB/Raw/TpiStream.cpp
index 7ff1e3d..8b44ec1 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/TpiStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/TpiStream.cpp
@@ -269,3 +269,5 @@
 TpiStream::types(bool *HadError) const {
   return llvm::make_range(TypeRecords.begin(HadError), TypeRecords.end());
 }
+
+Error TpiStream::commit() { return Error::success(); }