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

content/renderer/media/peer_connection_tracker.cc

Index: content/renderer/media/peer_connection_tracker.cc
diff --git a/content/renderer/media/peer_connection_tracker.cc b/content/renderer/media/peer_connection_tracker.cc
index 49ff5c49bbee1c9a7b690b3f30b800f99ffe5bae..18fc0508d45c6f56b387f71988477dd66d94b23e 100644
--- a/content/renderer/media/peer_connection_tracker.cc
+++ b/content/renderer/media/peer_connection_tracker.cc
@@ -94,7 +94,7 @@ static std::string SerializeMediaDescriptor(
   std::string result = "id: " + id;
   blink::WebVector<blink::WebMediaStreamTrack> tracks;
   stream.audioTracks(tracks);
-  if (!tracks.isEmpty()) {
+  if (!tracks.empty()) {
     result += ", audio: [";
     for (size_t i = 0; i < tracks.size(); ++i) {
       result += SerializeMediaStreamComponent(tracks[i]);
@@ -104,7 +104,7 @@ static std::string SerializeMediaDescriptor(
     result += "]";
   }
   stream.videoTracks(tracks);
-  if (!tracks.isEmpty()) {
+  if (!tracks.empty()) {
     result += ", video: [";
     for (size_t i = 0; i < tracks.size(); ++i) {
       result += SerializeMediaStreamComponent(tracks[i]);