Improving performance of notification panel

This might not directly fix b/187139139 but it's definitely
step in a good direction and we shouldn't check Resources
every time when calculating clock position.

Bug: 187139139
Test: Performance tests run on demand
before: https://android-build.googleplex.com/builds/abtd/run/L97900000900103160
after: https://android-build.googleplex.com/builds/abtd/run/L52500000900103665
Change-Id: I9ef13f957a31232287dcdb9c9848fa8431409377