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

content/renderer/media/canvas_capture_handler.cc

Index: content/renderer/media/canvas_capture_handler.cc
diff --git a/content/renderer/media/canvas_capture_handler.cc b/content/renderer/media/canvas_capture_handler.cc
index e289fd46dcec3610394a2e3f6dc2b627d18eb257..822da6ae379e205f5620fb10e7973eae0a7d8341 100644
--- a/content/renderer/media/canvas_capture_handler.cc
+++ b/content/renderer/media/canvas_capture_handler.cc
@@ -257,7 +257,7 @@ void CanvasCaptureHandler::AddVideoCapturerSourceToVideoTrack(
     blink::WebMediaStreamTrack* web_track) {
   std::string str_track_id;
   base::Base64Encode(base::RandBytesAsString(64), &str_track_id);
-  const blink::WebString track_id = base::UTF8ToUTF16(str_track_id);
+  const blink::WebString track_id = blink::WebString::fromASCII(str_track_id);

[kinuko, 2016/12/17 02:27:14]

Looks like str_track_id is ASCII-only

   blink::WebMediaStreamSource webkit_source;
   std::unique_ptr<MediaStreamVideoSource> media_stream_source(
       new MediaStreamVideoCapturerSource(