Tracks exception count by class name.

The goal is to figure out if it would be worth monitoring these
exceptions. If exception types are only caller issues like
SecurityException and IllegalArgumentException, it is probably not worth
it. If we can find NPE or internal exceptions it would be worth
uploading the exceptions through dropbox.

Test: unit test

Change-Id: I779d43a0e6ca1a33535b90809491675420a51726