Flags are to be used in new tests when creating tests that potentially
take a long time to run. Certain test suites are intended to be quick
and may skip certain long running tests.
New slow tests should check these flags and skip using GTEST_SKIP().
Bug: 311273599
Test: ./build.py x86-64 --debug
Change-Id: I4fc5a026f23f489bf2ad8b8a11dc467f550f0c5e