Tests for Runtime.*Memory()

The docs describe a condition we do not test for.
The freeMemory / totalMemory tests have been consolidated
into a single test and joined by an additional assertion for
maxMemory().

The test for freeMemory from OldRuntimeTest has been tidied
up and moved to RuntimeTest.

Bug: 15507122
Change-Id: I4343215fb7f6b441613e25d3844d67812f5b5e94
2 files changed