Call CalculatorInterface::CalculateString even for x86 Android testing

With this CL, CalculatorInterface::CalculateString is called just as a smoke test.
This is just a clean-up of unittest. Hence no behavior change is intended.

Patch from Tsuyoshi Matsuzaki.

BUG=none
TEST=compile


git-svn-id: http://mozc.googlecode.com/svn/trunk@480 a6090854-d499-a067-5803-1114d4e51264