Introduce perf tests for background text layout performance

Here is an example of perf score:

StaticLayout creation time
 1 Thread:  7,301,172
 2 Thread: 13,842,641
 4 Thread: 25,232,063

Bug: 37567215
Test: See above
Change-Id: I319abd5fe0861575649a1122c91f1949c6ad14d2