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

content/renderer/media/media_stream_video_source.cc

Index: content/renderer/media/media_stream_video_source.cc
diff --git a/content/renderer/media/media_stream_video_source.cc b/content/renderer/media/media_stream_video_source.cc
index ab1453fed9bb3c12922edc98e15080c5bf316bad..c95f429b466454e534878c674a5cc31578e43c46 100644
--- a/content/renderer/media/media_stream_video_source.cc
+++ b/content/renderer/media/media_stream_video_source.cc
@@ -500,7 +500,12 @@ bool MediaStreamVideoSource::FindBestFormatWithConstraints(
 
     // 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;
   }