Use explicit WebString <-> string16 conversion methods in media files

content/renderer/media/pepper_to_video_track_adapter.cc

Index: content/renderer/media/pepper_to_video_track_adapter.cc
diff --git a/content/renderer/media/pepper_to_video_track_adapter.cc b/content/renderer/media/pepper_to_video_track_adapter.cc
index 8535dca204bb3b8a56a675b9877887c52a6b67cd..5282026afc7d7bed9067dbe2be549a4b547411b3 100644
--- a/content/renderer/media/pepper_to_video_track_adapter.cc
+++ b/content/renderer/media/pepper_to_video_track_adapter.cc
@@ -257,7 +257,7 @@ bool PepperToVideoTrackAdapter::Open(MediaStreamRegistryInterface* registry,
   blink::WebMediaStreamSource webkit_source;
   blink::WebMediaStreamSource::Type type =
       blink::WebMediaStreamSource::TypeVideo;
-  blink::WebString webkit_track_id = base::UTF8ToUTF16(track_id);
+  blink::WebString webkit_track_id = blink::WebString::fromUTF8(track_id);
   webkit_source.initialize(webkit_track_id, type, webkit_track_id,
                            false /* remote */);
   webkit_source.setExtraData(writer);