ComparatorTest: Tweak.

This test was using static final arrays which were not
supposed to be modified by a test method.

This CL:

 - replaces them with unmodifiable Lists, so that accidental
   modification (such as in bug 139015474) is noticed.
 - makes them nonstatic, so that no heap is retained after
   the instance of ComparatorTest is garbage collected.

Bug: 139015474
Test: atest CtsLibcoreTestCases:libcore.java.util.ComparatorTest
Change-Id: I941d16cf8e487eaede629079e846f96d9e859b7c
1 file changed