Convert media metadata from UTF-16 to UTF-8 instead of ASCII.

CrasAudioHandler converts media metadata from UTF-16 to ASCII. This is
invalid if the metadata is non-ASCII, which it can be. This DCHECK
fails when converting and later CHECK fails trying to send over D-Bus.
Convert to UTF-8 instead.

Bug: 1059929
Change-Id: I367e6ab718a1e875a69fd551e8c2e5c68a00f139
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2096328Reviewed-by: Jenny Zhang <jennyz@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749020}

chromeos/audio/cras_audio_handler.cc

@@ -264,10 +264,10 @@ void CrasAudioHandler::MediaSessionMetadataChanged(
     return;
 
   const std::map<std::string, std::string> metadata_map = {
-      {"title", base::UTF16ToASCII(metadata->title)},
-      {"artist", base::UTF16ToASCII(metadata->artist)},
-      {"album", base::UTF16ToASCII(metadata->album)}};
-  const std::string source_title = base::UTF16ToASCII(metadata->source_title);
+      {"title", base::UTF16ToUTF8(metadata->title)},
+      {"artist", base::UTF16ToUTF8(metadata->artist)},
+      {"album", base::UTF16ToUTF8(metadata->album)}};
+  const std::string source_title = base::UTF16ToUTF8(metadata->source_title);
 
   // Assume media duration/length should always change with new metadata.
   fetch_media_session_duration_ = true;