Bug 1084010 - [Usage][Cost Control] Browser icon should not appear in Mo...

...bile App Usage list
Add a comment pointing to [bug 1084010 comment 0](https://bugzilla.mozilla.org/show_bug.cgi?id=1084010#c0) saying the discarded data will be automatically count as `residual data` calculated in... (put the file where is the calculus of the residual data).