Update Segment size if Cues size changes on repositioning
Update Segment size if Cues size changes on repositioning

Files created with Segment::CopyAndMoveCuesBeforeClusters can't be parsed by
libwebm because the Segment size was not updated to account for the change
in Cue size. Fixing that.

Change-Id: I993f63e5c279f131cd39c54bee40163da00b8cbd

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