derp
Only show ART information if switching from dalvik to ART

We do not want to confuse users with a big information dialog, if
they change from ART to dalvik as dalvik is still the official
solution, supported and considered safe.

Change-Id: I0ce4846e0bb751e87e5c410e668d4bc521380141

Patchset: 2
https://gerrit.omnirom.org/#/c/3698/