Do not make a getThreadTimeMicro() call when it is not needed. This was

accidentally changed with https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15080830

Bug: 193543224
Test: N/A no functionality change, just avoiding a method call
Change-Id: If4579e96cd5aab41a46f60b5133938e81d608cff