Update parsing for cpufreq events due to format change.

There seems to be an extra actual= argument in the android
trace files now. I've updated the parsing to make it more
lenient towards the accepted data. This should handle
both the new and old format.

I also created some tests for the cpufreq code.

BUG=trace-viewer:135

Review URL: https://codereview.appspot.com/7306064

git-svn-id: https://trace-viewer.googlecode.com/svn/trunk@208 0e6d7f2b-9903-5b78-7403-59d27f066143