Removed use of StringUtf8Micro and instead use an extra byte array
instance variable directly in the class. This allows the list returned
for repeated strings to be a String instead of a StringUtf8Micro
making the class compatible with existing code.

Removed PerfTimer.java which isn't used.

Change-Id: Ie6acfb40f98f59a48c1a795d86f715078f9611f5