Add ability to instantiate VideoEncoderSoftwareFallback in VP tests.

webrtc/modules/video_coding/codecs/test/videoprocessor_integrationtest.h

 /*
  *  Copyright (c) 2017 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 132 matching lines @@
   void PrintAndMaybeVerifyRateControlMetrics(
       int rate_update_index,
       const std::vector<RateControlThresholds>* rc_thresholds,
       const std::vector<int>& num_dropped_frames,
       const std::vector<int>& num_resize_actions);
   int TemporalLayerIndexForFrame(int frame_number) const;
   void ResetRateControlMetrics(int rate_update_index,
                                const RateProfile& rate_profile);
 
   // Codecs.
-  std::unique_ptr<cricket::WebRtcVideoEncoderFactory> encoder_factory_;
-  VideoEncoder* encoder_;
+  std::unique_ptr<VideoEncoder> encoder_;
   std::unique_ptr<cricket::WebRtcVideoDecoderFactory> decoder_factory_;
   VideoDecoder* decoder_;
 
   // Helper objects.
   std::unique_ptr<FrameReader> analysis_frame_reader_;
   std::unique_ptr<FrameWriter> analysis_frame_writer_;
   std::unique_ptr<IvfFileWriter> encoded_frame_writer_;
   std::unique_ptr<FrameWriter> decoded_frame_writer_;
   PacketReader packet_reader_;
   std::unique_ptr<PacketManipulator> packet_manipulator_;
@@ skipping 19 matching lines @@
   float target_size_key_frame_initial_;
   float target_size_key_frame_;
   float sum_key_frame_size_mismatch_;
   int num_key_frames_;
 };
 
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_CODECS_TEST_VIDEOPROCESSOR_INTEGRATIONTEST_H_