Implement FakeFileAccess.

Update embedder tests to simulate unavailable data and download requests.

Change-Id: I634fa89d2a0c859243e849752936da87568909f4
Reviewed-on: https://pdfium-review.googlesource.com/11890
Commit-Queue: Art Snake <art-snake@yandex-team.ru>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/testing/range_set.h b/testing/range_set.h
new file mode 100644
index 0000000..87cbee9
--- /dev/null
+++ b/testing/range_set.h
@@ -0,0 +1,45 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TESTING_RANGE_SET_H_
+#define TESTING_RANGE_SET_H_
+
+#include <set>
+#include <utility>
+
+class RangeSet {
+ public:
+  using Range = std::pair<size_t, size_t>;
+
+  RangeSet();
+  ~RangeSet();
+
+  bool Contains(const Range& range) const;
+
+  void Union(const Range& range);
+
+  void Union(const RangeSet& range_set);
+
+  bool IsEmpty() const { return ranges().empty(); }
+
+  void Clear() { ranges_.clear(); }
+
+  struct range_compare {
+    bool operator()(const Range& lval, const Range& rval) const {
+      return lval.first < rval.first;
+    }
+  };
+
+  using RangesContainer = std::set<Range, range_compare>;
+  const RangesContainer& ranges() const { return ranges_; }
+
+ private:
+  Range FixDirection(const Range& range) const;
+
+  bool IsEmptyRange(const Range& range) const;
+
+  RangesContainer ranges_;
+};
+
+#endif  // TESTING_RANGE_SET_H_