Subzero: Fix build problem against LLVM trunk.

pnacl-llvm/include/llvm/Support/DataStream.h

+//===---- llvm/Support/DataStream.h - Lazy bitcode streaming ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header defines DataStreamer, which fetches bytes of data from
+// a stream source. It provides support for streaming (lazy reading) of
+// data, e.g. bitcode
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifndef LLVM_SUPPORT_DATASTREAM_H
+#define LLVM_SUPPORT_DATASTREAM_H
+
+#include <memory>
+#include <string>
+
+namespace llvm {
+
+class DataStreamer {
+public:
+  /// Fetch bytes [start-end) from the stream, and write them to the
+  /// buffer pointed to by buf. Returns the number of bytes actually written.
+  virtual size_t GetBytes(unsigned char *buf, size_t len) = 0;
+
+  virtual ~DataStreamer();
+};
+
+std::unique_ptr<DataStreamer> getDataFileStreamer(const std::string &Filename,
+                                                  std::string *Err);
+}
+
+#endif  // LLVM_SUPPORT_DATASTREAM_H_