Ensure that selected video format is valid when resolving video-capture constraints.

content/renderer/media/media_stream_video_source.cc

 // Copyright 2014 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 "content/renderer/media/media_stream_video_source.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 
@@ skipping 482 matching lines @@
       return true;
     }
     std::string unsatisfied_constraint;
     const media::VideoCaptureFormats filtered_formats =
         FilterFormats(track_constraints, formats, &unsatisfied_constraint);
     if (filtered_formats.empty())
       continue;
 
     // A request with constraints that can be fulfilled.
     *fulfilled_constraints = track_constraints;
-    *best_format = GetBestCaptureFormat(filtered_formats, track_constraints);
+    media::VideoCaptureFormat best_format_candidate =
+        GetBestCaptureFormat(filtered_formats, track_constraints);
+    if (!best_format_candidate.IsValid())
+      continue;
+
+    *best_format = best_format_candidate;
     DVLOG(3) << "Found a track that matches the constraints";
     return true;
   }
   DVLOG(3) << "No usable format found";
   return false;
 }
 
 void MediaStreamVideoSource::OnStartDone(MediaStreamRequestResult result) {
   DCHECK(CalledOnValidThread());
   DVLOG(3) << "OnStartDone({result =" << result << "})";
@@ skipping 96 matching lines @@
       callback(callback) {
 }
 
 MediaStreamVideoSource::TrackDescriptor::TrackDescriptor(
     const TrackDescriptor& other) = default;
 
 MediaStreamVideoSource::TrackDescriptor::~TrackDescriptor() {
 }
 
 }  // namespace content