Do not cache the method name from PrettyMethod.

Restores parity with the cache that was present before the external API was
introduced.

Test: mmma art/
Test: mmma system/core/{libunwindstack,libbacktrace} and run host gtests
Bug: 119632407
Change-Id: If15114595513442b16fef47bb277bf43e781a658
1 file changed