Provide DIA implementation of DebugInfoPDB.

This implements DebugInfoPDB when the DIA SDK is present on the system.
Specifically, this means that the following conditions are met:
  1) You are building on Windows.
  2) You are building with MSVC.
  3) Visual Studio did not corrupt the installation of DIA due to a
     known issue with side-by-side installations of VS2012 and VS2013.
If all of these conditions are true, you will be able to pass a value
of PDB_Reader::DIA to PDB::createPdbReader().

There are no tests for this yet, as any test will be in the form of a
lit test which tests the llvm-pdbdump.exe, which still needs to be
rewritten in terms of this library.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228747 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/DebugInfo/PDB/DIA/DIADataStream.h

@@ -0,0 +1,33 @@
+//===- DIADataStream.h - DIA implementation of IPDBDataStream ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_PDB_DIA_DIADATASTREAM_H
+#define LLVM_DEBUGINFO_PDB_DIA_DIADATASTREAM_H
+
+#include "DIASupport.h"
+#include "llvm/DebugInfo/PDB/IPDBDataStream.h"
+
+namespace llvm {
+class DIADataStream : public IPDBDataStream {
+public:
+  explicit DIADataStream(CComPtr<IDiaEnumDebugStreamData> DiaStreamData);
+
+  uint32_t getRecordCount() const override;
+  std::string getName() const override;
+  llvm::Optional<RecordType> getItemAtIndex(uint32_t Index) const override;
+  bool getNext(RecordType &Record) override;
+  void reset() override;
+  DIADataStream *clone() const override;
+
+private:
+  CComPtr<IDiaEnumDebugStreamData> StreamData;
+};
+}
+
+#endif