added comment to fix VideoTrack::Seek
added comment to fix VideoTrack::Seek

Change-Id: I2a8b3e4ca92bdfd2d77c84ab970379d22a06e451

ericmckean/webm.libwebm,zofuthan/libwebm,felipebetancur/libwebm,kalli123/webm.libwebm,Suvarna1488/webm.libwebm,matanbs/webm.libwebm,reimaginemedia/webm.libwebm,jdm/libwebm,abwiz0086/webm.libwebm,zofuthan/libwebm,iniwf/webm.libwebm,kim42083/webm.libwebm,pcwalton/libwebm,gshORTON/webm.libwebm,kleopatra999/webm.libwebm,Maria1099/webm.libwebm,Acidburn0zzz/webm.libwebm,felipebetancur/libwebm,webmproject/libwebm,webmproject/libwebm,webmproject/libwebm