MediaStreamRecorder: enable in Android (including linking libwebm)

media/capture/webm_muxer.cc

Index: media/capture/webm_muxer.cc
diff --git a/media/capture/webm_muxer.cc b/media/capture/webm_muxer.cc
index 5e569bcb8ecaa24859209b76ae368310e004887d..939cb397ca1569bfc431529d4d9f7fe6aa63ebad 100644
--- a/media/capture/webm_muxer.cc
+++ b/media/capture/webm_muxer.cc
@@ -45,8 +45,10 @@ void WriteOpusHeader(const media::AudioParameters& params, uint8* header) {
     header[OPUS_EXTRADATA_NUM_STREAMS_OFFSET] = params.channels();
     header[OPUS_EXTRADATA_NUM_COUPLED_OFFSET] = 0;
     // Set the actual stream map.
-    memcpy(header + OPUS_EXTRADATA_STREAM_MAP_OFFSET,
-           kOpusVorbisChannelMap[params.channels() - 1], params.channels());
+    for (int i = 0; i < params.channels(); ++i) {
+      header[OPUS_EXTRADATA_STREAM_MAP_OFFSET + i] =
+          kOpusVorbisChannelMap[params.channels() - 1][i];
+    }
   } else {
     header[OPUS_EXTRADATA_CHANNEL_MAPPING_OFFSET] = 0;
   }