Add pdf_unittests target.

pdf/chunk_stream_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "pdf/chunk_stream.h"
+
 #include "testing/gtest/include/gtest/gtest.h"
-#include "testing/gtest_mac.h"
 
-int main(int argc, char* argv[]) {
-  ::testing::InitGoogleTest(&argc, argv);
-  return RUN_ALL_TESTS();
+namespace chrome_pdf {
+
+TEST(ChunkStreamTest, Simple) {
+  ChunkStream stream;
+  stream.Preallocate(1000);
+  EXPECT_FALSE(stream.IsRangeAvailable(100, 500));
 }
+
+}  // namespace chrome_pdf