Re-enable Vp9FlexModeRefCount

webrtc/video/video_send_stream_tests.cc

 /*
  *  Copyright (c) 2013 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.
  */
 #include <algorithm>  // max
@@ skipping 2262 matching lines @@
 
     void InspectHeader(const RTPVideoHeaderVP9& vp9_header) override {
       if (frames_sent_ > kNumFramesToSend)
         observation_complete_.Set();
     }
   } test;
 
   RunBaseTest(&test);
 }
 
-#if !defined(MEMORY_SANITIZER)
-// Fails under MemorySanitizer:
-// See https://code.google.com/p/webrtc/issues/detail?id=5402.
 TEST_F(VideoSendStreamTest, Vp9FlexModeRefCount) {
   class FlexibleMode : public Vp9HeaderObserver {
     void ModifyVideoConfigsHook(
         VideoSendStream::Config* send_config,
         std::vector<VideoReceiveStream::Config>* receive_configs,
         VideoEncoderConfig* encoder_config) override {
       encoder_config->content_type = VideoEncoderConfig::ContentType::kScreen;
       vp9_settings_.flexibleMode = true;
       vp9_settings_.numberOfTemporalLayers = 1;
       vp9_settings_.numberOfSpatialLayers = 2;
     }
 
     void InspectHeader(const RTPVideoHeaderVP9& vp9_header) override {
       EXPECT_TRUE(vp9_header.flexible_mode);
       EXPECT_EQ(kNoTl0PicIdx, vp9_header.tl0_pic_idx);
       if (vp9_header.inter_pic_predicted) {
         EXPECT_GT(vp9_header.num_ref_pics, 0u);
         observation_complete_.Set();
       }
     }
   } test;
 
   RunBaseTest(&test);
 }
-#endif
 
 }  // namespace webrtc