Simplify getEffectMultiplier.

Both return cases were same, except for some overflow conditions.
Fix typo in comments.
Cleanup:  Don't call <environment obj>.get().

mEnvironment.get() is redundant.  Switch the call to resemble the
surrounding environment get() calls, instead.
Document the return value of getEffectMultiplier.
Merge remote-tracking branch 'jordan-ayers/topic/misc-cleanup'