FileWrapper[Impl] modifications and actually remove the "Impl" class.

webrtc/modules/video_coding/utility/ivf_file_writer_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 106 matching lines @@
         WriteDummyTestFrames(kWidth, kHeight, kNumFrames, use_capture_tims_ms));
     EXPECT_TRUE(file_writer_->Close());
 
     std::unique_ptr<FileWrapper> out_file(FileWrapper::Create());
     ASSERT_EQ(0, out_file->OpenFile(file_name_.c_str(), true));
     VerifyIvfHeader(out_file.get(), fourcc, kWidth, kHeight, kNumFrames,
                     use_capture_tims_ms);
     VerifyDummyTestFrames(out_file.get(), kNumFrames);
 
     out_file->Flush();
-    EXPECT_EQ(0, out_file->CloseFile());
+    out_file->CloseFile();
 
     bool file_removed = false;
     for (int i = 0; i < kMaxFileRetries; ++i) {
       file_removed = remove(file_name_.c_str()) == 0;
       if (file_removed)
         break;
 
       // Couldn't remove file for some reason, wait a sec and try again.
       rtc::Thread::SleepMs(1000);
     }
@@ skipping 56 matching lines @@
   const uint8_t fourcc[4] = {'H', '2', '6', '4'};
   RunBasicFileStructureTest(kVideoCodecH264, fourcc, false);
 }
 
 TEST_F(IvfFileWriterTest, WritesBasicH264FileMsTimestamp) {
   const uint8_t fourcc[4] = {'H', '2', '6', '4'};
   RunBasicFileStructureTest(kVideoCodecH264, fourcc, true);
 }
 
 }  // namespace webrtc