Support alpha channel recording for VPX in MediaRecorder

media/muxers/webm_muxer_fuzzertest.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 <stddef.h>
 #include <stdint.h>
 
 #include <random>
 
 #include "base/bind.h"
@@ skipping 47 matching lines @@
     base::RunLoop run_loop;
     run_loop.RunUntilIdle();
 
     int num_iterations = kMinNumIterations + rng() % kMaxNumIterations;
     do {
       if (input_type.has_video) {
         // VideoFrames cannot be arbitrarily small.
         const auto visible_rect = gfx::Size(16 + rng() % 128, 16 + rng() % 128);
         const auto video_frame = VideoFrame::CreateBlackFrame(visible_rect);
         const auto is_key_frame = rng() % 2;
-        muxer.OnEncodedVideo(WebmMuxer::VideoParameters(video_frame),
-                             base::MakeUnique<std::string>(str),
-                             base::TimeTicks(), is_key_frame);
+        const auto has_alpha_frame = rng() % 4;
+        muxer.OnEncodedVideo(
+            WebmMuxer::VideoParameters(video_frame),
+            base::MakeUnique<std::string>(str),
+            has_alpha_frame ? base::MakeUnique<std::string>(str) : nullptr,
+            base::TimeTicks(), is_key_frame);
         base::RunLoop run_loop;
         run_loop.RunUntilIdle();
       }
 
       if (input_type.has_audio) {
         const ChannelLayout layout = rng() % 2 ? media::CHANNEL_LAYOUT_STEREO
                                                : media::CHANNEL_LAYOUT_MONO;
         const int sample_rate =
             kSampleRatesInKHz[rng() % arraysize(kSampleRatesInKHz)];
 
         const AudioParameters params(
             media::AudioParameters::AUDIO_PCM_LOW_LATENCY, layout, sample_rate,
             16 /* bits_per_sample */, 60 * sample_rate);
         muxer.OnEncodedAudio(params, base::MakeUnique<std::string>(str),
                              base::TimeTicks());
         base::RunLoop run_loop;
         run_loop.RunUntilIdle();
       }
     } while (num_iterations--);
   }
 
   return 0;
 }