[pdb] Refactor library to more clearly separate reading/writing

Reviewed By: amccarth, ruiu
Differential Revision: https://reviews.llvm.org/D22693

llvm-svn: 277019
diff --git a/llvm/lib/DebugInfo/PDB/Raw/ModInfo.cpp b/llvm/lib/DebugInfo/PDB/Raw/ModInfo.cpp
index 89a03ec..7b77bcd 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/ModInfo.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/ModInfo.cpp
@@ -27,7 +27,7 @@
 
 ModInfo::~ModInfo() {}
 
-Error ModInfo::initialize(StreamRef Stream, ModInfo &Info) {
+Error ModInfo::initialize(ReadableStreamRef Stream, ModInfo &Info) {
   StreamReader Reader(Stream);
   if (auto EC = Reader.readObject(Info.Layout))
     return EC;