mkvparser: quiet static analysis warnings
mkvparser: quiet static analysis warnings

in ParseContentEncodingEntry() the elements are parsed twice in the
loop, once to gather the count and a second time to parse the entries
and store them.

BUG=webm:1616

Change-Id: I96f2f53d133fed40deb5d641bde49e80c31427d8

webmproject/libwebm,webmproject/libwebm,webmproject/libwebm