Replace usage of WebVector::isEmpty with WebVector::empty().

content/renderer/media_recorder/media_recorder_handler.cc

Index: content/renderer/media_recorder/media_recorder_handler.cc
diff --git a/content/renderer/media_recorder/media_recorder_handler.cc b/content/renderer/media_recorder/media_recorder_handler.cc
index 9cc45602ffe7e4ce4d5168815c1848651ac9a9eb..fa6441a7a97a2c346bb493ef72182e3a38fe034e 100644
--- a/content/renderer/media_recorder/media_recorder_handler.cc
+++ b/content/renderer/media_recorder/media_recorder_handler.cc
@@ -167,18 +167,17 @@ bool MediaRecorderHandler::start(int timeslice) {
   media_stream_.videoTracks(video_tracks_);
   media_stream_.audioTracks(audio_tracks_);
 
-  if (video_tracks_.isEmpty() && audio_tracks_.isEmpty()) {
+  if (video_tracks_.empty() && audio_tracks_.empty()) {
     LOG(WARNING) << __func__ << ": no media tracks.";
     return false;
   }
 
   const bool use_video_tracks =
-      !video_tracks_.isEmpty() && video_tracks_[0].isEnabled() &&
+      !video_tracks_.empty() && video_tracks_[0].isEnabled() &&
       video_tracks_[0].source().getReadyState() !=
           blink::WebMediaStreamSource::ReadyStateEnded;
   const bool use_audio_tracks =
-      !audio_tracks_.isEmpty() &&
-      MediaStreamAudioTrack::From(audio_tracks_[0]) &&
+      !audio_tracks_.empty() && MediaStreamAudioTrack::From(audio_tracks_[0]) &&
       audio_tracks_[0].isEnabled() &&
       audio_tracks_[0].source().getReadyState() !=
           blink::WebMediaStreamSource::ReadyStateEnded;