[pdb] Add unit tests for PDB MappedBlockStream and zero copy

Differential Revision: http://reviews.llvm.org/D20837
Reviewed By: ruiu

llvm-svn: 271346
diff --git a/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
index acc92f9..34d1671 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
@@ -14,7 +14,8 @@
 using namespace llvm;
 using namespace llvm::pdb;
 
-MappedBlockStream::MappedBlockStream(uint32_t StreamIdx, const PDBFile &File) : Pdb(File) {
+MappedBlockStream::MappedBlockStream(uint32_t StreamIdx, const IPDBFile &File)
+    : Pdb(File) {
   if (StreamIdx >= Pdb.getNumStreams()) {
     StreamLength = 0;
   } else {
@@ -119,3 +120,7 @@
   return Error::success();
 
 }
+
+uint32_t MappedBlockStream::getNumBytesCopied() const {
+  return static_cast<uint32_t>(Pool.getBytesAllocated());
+}